Each challenge section will have the following information. Note that I skipped UAC (see UBC effectively) and the Day challenges - as you can always just repeat them if you think you can do significantly better than the last time, and they don't take long enough to bother scheduling them, unlike challenge series that will often take weeks or months to complete. And the implied ordering and commentary on each series is generally for completing the series, some can be profitably be started much earlier and a portion of the benefits gained without needing the progress needed to do later entries in the series, for those series that get significantly harder the more you have already done.

One special note as mentioned in the comments is doing a single UBC (or UAC) to unlock the Crystal Factory is probably one of the most critical things to do early in the game - the entry below for UBC is considering when to do UBC2-50 rather than when to pick up that first one (which many new starter guides will cover in better detail that I could here).

Reward: What the main long-term reward of the challenge is (ignoring clones/chocolate/GP/etc.)
Cap: How many of these can be done while increasing the main reward
Prerequisite challenges: Any challenges that are either mandatory (in-game requirement) or speed things up so much they are virtually required
Beneficial challenge rewards: Challenge rewards that will speed up this challenge series, but are not absolutely necessary (in some cases challenge series have circular benefits with each other) - note indirect boosts via raising clones, pet growth, crystal power are not considered here, and I have skipped mentioned UCC here as everything would be helped by the rewards that in some way (if they can be done after it).

Essential/Required for: Challenge series that either require in-game this challenge series (or some of them) to be done, or are made much faster and easier by doing this first
Helpful for: Challenge series that will be helped by the reward but not to the point it seems essential to do this first. Again this only considers the reward for the challenge, not the incidental base power (pet growth, might boost gain, etc.) you are getting as a side effect of doing the challenge, and I have skipped mentioning UCC here as everything helps that in some way.

Estimated duration (early game): An extremely rough idea of how long each challenge is likely to take - especially rough for early game as you gain in so many areas so quickly that the time to do a challenge can drop massively even during the course of doing one series of challenges in some cases. Generally this time would presume you have done any challenge series listed as "Essential/Required" but not much else, but for all but the presumed earliest challenge series having done at least 1-2 challenge series before it (so with a few pets, training 1-capped, etc.)
Estimated duration (mid game): A rough estimate of how long each challenge will take having done about half the challenge series in the game (assuming not too much time spent speed running, growing pets outside challenges, crystal power farming, etc.) - probably including most or all of the "beneficial challenges" (apart from the circular ones), and time to build up a decent roster of pets with a fair amount of growth, might boost, crystal power, etc.
Estimated duration (late game): A rough estimate of how long each challenge will take having done most challenges in the game (of course faster speeds will be possible if micromanaging heavily, or if buying divinity, or stocking up tickets, etc.), with most pets unlocked and evolved and with high growth, lots of crystal power, light clones, RTI permanent levels, etc. Note that what counts as late game expands as you go further down the list - after completing UCC and doing NRC+5 it took me 72 hours, a couple of years later (with RTI added, loads of OC done, and all the normal growth of stuff) I now reach the same point after 6 hours.

Comments: Some further waffle about when it might be best to do this challenge, what benefits it has or what things are best to do before it, etc.

Reward: Up to 50 free might levels whenever Might unlocks (60 with UCC rewards)
Cap: 25 (reward will rise to 30 with UCC4 done)
Prerequisite challenges: None
Beneficial challenge rewards: AAC, CBC

Essential/Required for: 1kC, NDC, GSC, CBC, UCC, TMC, NDMC, UGC, LCC
Helpful for: PBC

Estimated duration (early game): 12 hours
Estimated duration (mid game): 6 hours
Estimated duration (late game): 4 hours

Comments: Essential for kickstarting might growth early on when you don't have the clones to level it manually, as well as making your rebirths much more powerful (both by increasing all stats via Total Might, and making unleash duration longer), so really want to do these before doing anything that is basically a series of might rebirths (except UBCs due to this challenge reward being specifically disabled) - of course most of those have doing at least one of these as an in-game prequisite, but beyond that they will be significantly easier with all of these done.

Reward: Increase pet campaign rewards by up to 100%
Cap: 20
Prerequisite challenges: None
Beneficial challenge rewards: NDC

Essential/Required for: UBC, CBC, NRC, PGC
Helpful for: DRC, 1kC, UUC, UPC, GSC, BHC, NDC, PMC, CPC, PBC, UCC, 1kBHC, UGC

Estimated duration (early game): 48 hours
Estimated duration (mid game): 24 hours
Estimated duration (late game): 16 hours

Comments: Definitely one of the earlier challenge series to do once you have enough pets/pet growth just because of upgrading the pet growth campaign feedback (which will help with almost all challenges via pet multiplier), but also due to the flexibility of pet campaigns the reward is helpful in almost every other challenge series - although maybe not enough for some to spare pets from more long term boosting campaigns to run divinity/multiplier campaigns that can often speed up the current rebirth/challenge a bit, at least until your pet roster gets fuller anyway.

Even in UBCs where the pet multiplier is disabled, the boost to the GP campaign and how much the early rebirths speed up with the faster rate you get extra creation speed (and then build speed, etc.) means it is still a major help there.

The UPC reward is also often doubled in effect as well on any campaigns whose rewards increase as growth/stats increase - your pets are higher base growth due to the boost to the pet growth campaign accumulated over time, but the rewards of the campaign are boosted as well (or the maximum can be achieved with a shorter campaign duration). Of course eventually you end up capping the campaign stat requirements in a matter of seconds during normal play, but you still get to that point earlier the sooner you do UPC.

Reward: Increase the effect of monuments by up to 50%
Cap: 40
Prerequisite challenges: None
Beneficial challenge rewards: BHC, NDC, NDMC

Essential/Required for: None
Helpful for: DRC, GSC, NDC, 1kC, NRC, PBC, UBC, NDMC, 1CCC, LCC, PGC

Estimated duration (early game): 12-72 hours (1st to 40th)
Estimated duration (mid game): 1-5 hours (1st to 40th)
Estimated duration (late game): 0.1-0.5 hours (1st to 40th)

Comments: A challenge series that probably could be considered fairly early on given most are at least as easy as a UUC, and even the last five only require a few black holes with a couple of upgrades, so aren't going to take much longer than a BHC.

In terms of benefits for other challenges the boosts in monuments (and therefore stats) will give a moderate boost in a fairly wide range of situations, every now and then allowing one more god to be taken down during a rebirth (or reaching the same god in a slightly shorter time).

Reward: Increased clone might building speed by up to 200% (250% after UCC rewards)
Cap: 40 (reward will rise to 50 with UCC14 done)
Prerequisite challenges: DRC
Beneficial challenge rewards: AAC, CBC

Essential/Required for: PMC, NRC, UCC, UGC, LCC, USC
Helpful for: NDMC, UBC, PGC

Estimated duration (early game): 16 hours
Estimated duration (mid game): 8 hours
Estimated duration (late game): 5 hours

Comments: Difficult to place in the order - it will get faster as your base power boosters (pets/might boost/crystal power) grow more than anything, and is only really needed before the likely to be quite late challenges that require lots of might levels to do efficiently, but is also pretty nice to have during the mid-game to make building might levels manually more effective (especially during overnight rebirths), and after the very early game the power you gain is fairly gradual so doing it one or two challenge series later isn't going to make much difference to the time taken.

So I could see doing it early as a continuation of DRC might unlocks to boost might without really considering the reward as useful in the short term, or leave it until just before doing PMCs if you don't find yourself wanting to put clones into might much.

Once you start putting a substantial proportion of your clones to level might up manually it makes a huge difference - even just half your clones in the might tab with this series of challenges done effectively doubles the number of clones you have in effect. Of course you will probably want to prepare by diverting some GP into build speed before starting these (or do it after CPCs so your CP is relatively high).

Reward: Increases effect of crystal power by up to 100% (120% after UCC rewards)
Cap: 26 (effective count will rise to 31 with UCC20 done)
Prerequisite challenges: DRC
Beneficial challenge rewards: AAC, UPC, NDC (sometimes), CBC

Essential/Required for: NRC, UCC, UGC, LCC, USC
Helpful for: 1kC, NDC, PBC, NDMC, UBC, PGC

Estimated duration (early game): 16 hours
Estimated duration (mid game): 9 hours
Estimated duration (late game): 6 hours

Comments: Estimated durations are even more wonky/approximate than usual here due to the nature of the challenge - the first half of the challenges will be the same time as DRCs, many of the rest allow some monument building so will be more like 1kC/NDC (getting worse once upgrades are disabled), while there are two or three that will be even slower due to the complete or near complete blocks of monument building.

Once the crystal power you have accumulated is reasonably high the reward can be approximated to doubling all your useful stats at any time (except for challenges that lock away GP and/or CP anyway), as well as the effect of increasing your creation and build speeds over time (or saving the GP you might otherwise have spent on them, whichever way you want to look at it).

Reward: Decreased time/score needed to reach each training/fighting achievement by up to 50%, 50% increase in multiplier awarded for each achievement gained (55% after UCC rewards)
Cap: 50 (reward will rise to 55 with UCC20 done)
Prerequisite challenges: UUC
Beneficial challenge rewards: None (itself)

Essential/Required for: UCC
Helpful for: DRC, 1kC, GSC, NDC, CBC, NRC, PBC, UBC, NDMC, UGC, 1CCC, LCC, PGC

Estimated duration (early game): 42-84 hours
Estimated duration (mid game): 42-84 hours
Estimated duration (late game): 42-84 hours

Comments: AACs are a fairly flexible challenge - as soon as you can build a universe in a couple of days and have 1 capped your trainings (or near enough you can spare the clones to run them at bb for a few days) you could start doing them, or you could leave them for ages as they aren't really necessary for anything, just nice for quite a few.

They also don't have a completion bonus so you could also do them in bits of pieces - either when you need a break from being active, or at the tail end of a P Baal climb to push a few more for that extra pet, then do something else rather than do them all at once. Whenever you do them they will take up the same amount of time as the only thing that makes them faster is your previous AACs.

The reward is broadly useful as many challenges gain from the increase stats (both current and through increased rebirth multipliers), but part of the benefit is somewhat patchy depend on exact rebirth times - basically the boosts from each "layer" of achievements starts after half the time has passed - so tier 1 is 15s instead of 30s, tier 2 is 2m30 instead of 5 minutes, tier 3 is 25m instead of 50m, tier 4 is 2h06 instead of 4h12, tier 5 is 8h25 instead of 16h50 minutes - each tier then runs for 1h35 (assuming Improved Next At is in use), so the early tiers overlap each other and creates a vaguely smooth increase for the first few hours, but later there can be no difference between having all the AACs or none in which achievements you have (6-8 hours for example), or a very substantial increase (3-4 hours, 10-16 hours)*. Of course even when the number of achievements is the same there is still the +50% boost in their effect (which has a double effect as it affects the size of both current and rebirth multipliers)

Overall it is a tough one - there is no advantage to waiting for your power to grow, and the reward is fairly decent and has fairly broad usefulness in other challenges, but it is one of the longest challenge series to complete (if not the longest), so there is the opportunity cost of what other challenges could have been done in the same time.

*The mutlipliers also take the form 1x, 3x, 5x, 5x, 5x, 5x which are added to each other, so the fourth and later tiers of achievements have somewhat less of an impact than the early tiers

Reward: Increased planet level to 50 (60 after UCC rewards, and then more from DBC score and ChP bonus)
Cap: 45 (reward will rise to 55 with UCC14 done)
Prerequisite challenges: None
Beneficial challenge rewards: NDC

Essential/Required for: PMC, NRC, UCC
Helpful for: NDMC

Estimated duration (early game): 10 hours
Estimated duration (mid game): 1 hours
Estimated duration (late game): <0.5 hours

Comments: Although the reward isn't very important early on (until you start needing powersurge, or have enough clones to spare to level it up for the extra stat bonus), doing UUCs early can work as a challenge-productive way of rising through P Baals if done while these challenges still take quite a few hours to do - if done later they will effectively just be might rebirth (or faster) challenges, just with the difference that every rebirth is a new challenge.

Reward: Increased base DivGen conversion rate by up to 50, 15% discount for buying creations (60 and 18% after UCC rewards)
Cap: 25 (reward will rise to 30 with UCC10 done)
Prerequisite challenges: DRC
Beneficial challenge rewards: AAC, UPC, GSC, CBC, TMC

Essential/Required for: UCC, USC
Helpful for: UUC, UPC, GSC, BHC, CBC, NRC, PBC, UBC, 1kBHC, UGC, 1CCC, LCC, PGC

Estimated duration (early game): 20 hours
Estimated duration (mid game): 8 hours
Estimated duration (late game): 4 hours

Comments: I generally found these are similar to 1kCs in difficulty once you can do them (having 50+ CC), as it will also get faster as your base power boosters (pets/might boost/crystal power) grow more than anything, and in both cases you can make some but not many monuments/upgrades.

After the very early game the power you gain is fairly gradual so doing it one or two challenge series later isn't going to make much difference to the time taken, so I would be tempted to do them relatively early as they benefit most other challenges due to the divinity boost - especially if you haven't climbed a huge amount of P Baals yet.

Equally you can wait until higher CC (or much, much higher) but each doubling of your CC isn't going to even double the monuments/upgrades you create due to the increasing cost each time, so it isn't like you are going to jump up more than the occasional extra god per rebirth by having more CC (of course you will also likely be getting more base power while getting the GP to buy it, which will also make it faster as well)

Reward: Decrease cost of BH and BHU by 80%, increase passive GP by up to 200%
Cap: 40
Prerequisite challenges: UUC
Beneficial challenge rewards: NDC, UPC

Essential/Required for: UCC, GPC, UGC, USC
Helpful for: PBC, NDMC, LCC

Estimated duration (early game): 16 hours
Estimated duration (mid game): 2 hours
Estimated duration (late game): <1 hour

Comments: Although the reward isn't important for completing many challenges, it is probably worth doing these before certain long rebirth challenges (AACs, PMCs, NRCs) for the passive GP increase.

Similar to UUCs, if you do the BHC challenge series relatively early it can work as a challenge-productive way of rising through P Baals if done while these challenges still take quite a few hours to do - if done later they will effectively just be might rebirth (or faster) challenges, just with the difference that every rebirth is a new challenge.

Conversely I could easily see putting them off until immediately before starting AACs if not done early as nothing else is really going to benefit much from them - even if you complete a challenge just before leaving the game overnight it will only occasionally be in a position where you have time to build a bunch of Black Holes to leave earning a few extra GP (and you often could have earnt a similar amount of extra GP by doing a quick extra rebirth/rebuild instead of taking the time to set them up)

Reward: Decrease the time to clear a dungeon room by up to 20%, increase max rooms per delve to 60.
Cap: 20
Prerequisite challenges: None
Beneficial challenge rewards: UBC, PGC

Essential/Required for: None
Helpful for: None

Estimated duration (early game): 24-96 hours (1st to 20th)
Estimated duration (mid game): 18-48 hours (1st to 20th)
Estimated duration (late game): 12-30 hours (1st to 20th)

Comments: Rather than challenges when to do this is mostly derived from your progress in dungeons as more teams going to deeper levels and difficulties is almost the only factor in how long it will take (due to the multiplicative nature of the bonus from doing dungeons, as opposed to the one-off additive nature of increased pet strength or amount of monuments built). The benefits are also limited to dungeons - so only indirectly benefiting other challenges where stats that can be boosted by equipment by accumulating inventory faster.

Reward: Increase the effect of Total Might by up to 100%
Cap: 25
Prerequisite challenges: DRC
Beneficial challenge rewards: 1kC, 1kBHC (at least one)

Essential/Required for: None
Helpful for: NDC, PBC, NRC, NDC, GSC, NDMC, UGC, LCC, UBC, PGC

Estimated duration (early game): 10-48 hours (1st to 25th)
Estimated duration (mid game): 4-16 hours (1st to 25th)
Estimated duration (late game): 3-10 hours (1st to 25th)

Comments: Depending on when you do these you might just be doing might rebirths for the 700 DRC "free" might levels and immediately rebirth, or if done a bit later once you have clones for it and have done the 1kC series then rebirths in the 2-4 hour range will tend to be faster - the exact duration depends on how much faster you can manually build might compared to this 442/hour base value.

While not essential for your progress in the challenges if you are planning to do more substantial rebirths where your clones increase might levels for a while after it is unlocked it might be useful to also have done CPC and other crystal factory boosting challenges before this one - as it is one of the rare challenge series where you can efficiently complete the challenge series with rebirths while building up a decent amount of Crystal Power.

Reward: Up to 50 "virtual" extra might levels applied on top of the existing might from DRC or earned by clones (60 after UCC rewards)
Cap: 25 (count will rise to 30 with UCC20 done)
Prerequisite challenges: DRC, UPC
Beneficial challenge rewards: GSC, NDC, AAC, 1CCC?

Essential/Required for: UBC, UCC, PGC
Helpful for: DRC, 1kC, GSC, NDC, CBC, PMC, NRC, PBC, NDMC, UGC, LCC

Estimated duration (early game): 96 hours
Estimated duration (mid game): 36 hours
Estimated duration (late game): 18 hours

Comments: Probably a safe bet for a mid-game challenge series whose reward becomes very useful once you have enough clones to start sending them to the Might tab in numbers and for a large chunk of most rebirths, particularly for challenges that really need many hundreds of levels in might like NRC and PMC.

Because each might level is slower than the previous one the virtual levels from this tacked on to what you have earned become worth many times as much as the free levels from DRC in such situations (of course both are nice combined in some situations like might rebirth based challenges where you don't have time to put clones on the might tab).

There is also the special case of UBC where the DRC reward is disabled, but CBC works - this means unleash is 55 seconds instead of 5 seconds (and you are unlikely to spend much clone time raising it during each rebirth), among other things.

In terms of prerequisites UPC for the GP campaign seems fairly clear, especially if done before the late game (where you will jump up quite a lot of gods every rebirth anyway) - it makes the first few rebirths much more productive when you can buy creation speed boosts every rebirth, and then getting to build speed boosts faster means you climb gods faster to reach the bb creation multiplier target in less rebirths.

DRCs are probably even more of a requirement for the way they build your might boost right from the first rebirth, which again helps via pushing you up through the gods much faster, as well as the direct stat boosting effects of the might levels during that current rebirth.

As a special note I don't think doing CBCs extremely early on for the clones is a good idea at all - with neglible pet growth, might boost, no DRCs, etc., you could do a UBC in about the same amount of time as a CBC, and could spend the 100 GP side reward on 40k clones instead of the getting the 20k clone side reward from this challenge, and would be saving yourself time later once CBCs become significantly quicker and easier than UBCs.

Reward: Increased UB cycle time by up to 20% (25% with 20 UCCs done to unlock 21st-25th)
Cap: 20 (25 with 20 UCCs done)
Prerequisite challenges: 1kC, UUC, UPC, GSC
Beneficial challenge rewards: AAC, NDC, CBC, PMC, CPC, UCC, TMC, UBV2C, NDMC

Essential/Required for: MCC
Helpful for: PMC, CPC, PBC, 1kBHC, UGC, LCC, USC

Estimated duration (early game): 240+ hours (NRC+5: not available)
Estimated duration (mid game): 48 hours (NRC+5: not available)
Estimated duration (late game): 12 hours (NRC+5: 72 hours)

Comments: Increasing the UB spawn rate means both faster divinity gain and faster crystal production, so it helps with most of the challenges that rebirth later than might unlock (and even for some of those it causes a second wave of UBs with three times the divinity to appear a few minutes after might unlocks, so might still be useful) - either directly because of more divinity (and monuments), or indirectly through energy because faster and bigger crystals give a number of boosts (or for CPC directly through faster rate of CP gain).

Conversely defeating Baal in a single rebirth from a standing start can be very time consuming until you have lots of other challenge rewards, and lots of pets, pet growth, crystal power, might boost, clones, build speed, etc., so while in theory this challenge can be cleared at any point once UBs can be killed basically, it is almost certainly best to leave it fairly late in the order of challenges, my guideline would probably be under 2 days, i.e. once all the achievement related boosts have been gained assuming you have done all AACs, and with all or nearly all of the UB kill counts at 9 or higher, so you don't spend any/much time "suwesh"ing over the finish line from a mix of UB kill boosts and further slow additive grinding upwards of monuments/planetsurge/might levels, etc.

Once the UCC challenge series is complete five more of these are unlocked but require going 1 P Baal extra each time - at the time I did them I was doing regular NRCs in 10-12 hours, NRC+1 took about 18 hours, NRC+2 was 24h, NRC+3 about 36h, NRC+4 about 2 days and NRC+5 nearly 3 days.

Reward: Increased energy dropped by UB by up to 100% (120% after UCC rewards)
Cap: 50 (count will rise to 60 with UCC7 done)
Prerequisite challenges: 1kC, UUC, UBV2C
Beneficial challenge rewards: CBC, NRC

Essential/Required for: UCC, CPC, MCC
Helpful for: NRC, 1kBHC, LCC, USC, UBC, PGC

Estimated duration (early game): 48 to 240+ hours (1st to 50th)
Estimated duration (mid game): 14 to 48 hours
Estimated duration (late game): 10 to 22 hours

Comments: Probably a mid-late game challenge which requires plenty of clones, especially after the relatively low target early challenges are done - for levelling up planet surge and the stat boosting might levels to help kill the UBv2s.

While these presumably can feasibly be done without bbing planetsurge or not killing all five UBv2s, having half or third of the speed of planetsurge growth, or dropping the x6 multiplier from ItRtG v2 will extend the run time of each challenge signficantly - not as much as by x2 or x6, because the UB kill bonus stacks multiplicatively, so you can effectively "suwesh" your way to the target of each challenge no matter how far short you fall once the bonuses start dropping to their minimum levels (after 9 kills of each). However doing this for a significant part of the 50 of these challenges is not likely to be the best option unless you need a challenge you can just leave running for days once it is set up.

Also as noted by Ibn Battuta in the comments, UBV2C boosts your planet multiplier a lot, so now should probably be considered a prerequisite for this challenge.

In terms of the circular reward with NRCs probably doing the NRCs first is likely to make more difference - on long NRC runs extra energy and thus crystals to upgrade aren't really going to make a huge difference due to the multiply diminishing returns (due to the massively rise cost of upgrading to the next level combined with the additive nature of the crystal bonuses making each extra level have less impact), whereas the NRC reward will mean you kill 5 sets of UBs for every 4 you would have killed.

As with some of the other long normal rebirth challenges (particularly AAC), it might make sense to do some of these challenges as part of a P Baal climb, possibly splitting them up and doing the series in multiple groups at appropriate times when you have gained enough power or rewards from other challenges to push further.

Reward: Reduces clones needed to build crystals by up to 50%, and reduces time taken by 25% (60%, 30% after UCC rewards)
Cap: 25 (count will rise to 30 with UCC20 done)
Prerequisite challenges: PMC
Beneficial challenge rewards: NRC

Essential/Required for: UCC, MCC
Helpful for: CBC, UBC, PGC

Estimated duration (early game): 18 to 48 hours (1st to 25th)
Estimated duration (mid game): 9 to 36 hours
Estimated duration (late game): 6 to 30 hours

Comments: CPCs are somewhat of an oddity - doing them gives a reward that somewhat helps do more of them quicker (well it would if the target didn't grow each completion), but doesn't help much directly in other challenges - it allows you to build a couple more crystals from the first UB kill in a might rebirth scenario, but probably you will be doing these challenges after most or all of those are cleared. Conversely in longer rebirth challenges you will end up generating about 33% more crystals, but due to the diminishing returns of the conversions, this will only occasionally give you a one higher level crystal by the end, so the benefit there is limited as well.

In fact the primary benefit I found from this challenge series was that it boosted my accumulated CP by about a factor of four, due to the limited amount of CP you get if you are doing other challenges, which almost all have limited or no CP gains for various reasons (might rebirth not giving enough time, too few clones to kill UBs, lack of divinity to build crystals, or at the other extreme long rebirth challenges). This might not be so much the case for newer players (where crystals have been in the game since they started), but it still will presumably give a fairly hefty boost to stats, build and creation speeds.

Doing them early might have a benefit of the other part of the reward - reducing the clones needed in the crystal factories would be pretty helpful in the early-mid game while clones are always scarce, but the numbers involved are not that critical once you start having tens of millions of clones and above, at which point it will only be the faster crystal output that will be of interest.

The reduced clone count can also be useful for the later rebirths of CBCs/UBCs to build more crystals simultaneously (if you can get enough divinity for the materials for that many anyway).

Reward: Increased crystal power gain from sacrificing or holding crystals at rebith by up to 100%
Cap: 30
Prerequisite challenges: PMC, CPC, NRC
Beneficial challenge rewards: UCC20

Essential/Required for: None
Helpful for: UBC, PGC

Estimated duration (early game): 72 to 240 hours
Estimated duration (mid game): 28 to 81 hours
Estimated duration (late game): 28 to 81 hours

Comments: Probably a good challenge to do once the three pre-requisites that get you crystal energy from UBs faster, because the sooner it is done, the more CP you will accumulate for the rest of the game, and nothing else will help at all make this faster past that point.

Reward:New pet, and increased chance of the pet giving a GP each time it is fed
Cap: 25
Prerequisite challenges: None
Beneficial challenge rewards: BHC, 1k BHC, PBC, OC (BH related boosts)

Essential/Required for: None
Helpful for: UBC, PGC

Estimated duration (early game): 6 hours to 48 hours
Estimated duration (mid game): 1.5 hours to 12 hours
Estimated duration (late game): 5 seconds to 6 hours

Comments: With the initial requirement being 100 GP it is probably feasible to do this quite early to unlock an extra pet, and the rest either require a number of rebirths or could be done more passively if building up a fairly decent background level of GP income (building a number of Black Holes, killing all UBs, etc.) while certain other boosts such as getting 3 GP per P Baal and killing all UB V2s and then V4s will help chop off a large lump of each challenges target amount per rebirth, so also will be beneficial.

The final bonus effectively caps out around 1GP/3 hours so is a minor background benefit, but a bit more useful in GP reset challenges (presuming it doesn't get explicitly locked in them anyway).

Reward:Pets start at up to level 500 each rebirth
Cap: 25
Prerequisite challenges: None
Beneficial challenge rewards: UPC (indirectly)

Essential/Required for: None
Helpful for: 1kC, 1kBHC, UBC (?), PGC (?)

Estimated duration (early game): ? hours to ? hours
Estimated duration (mid game): ? hours to ? hours
Estimated duration (late game): 1 second

Comments: Really the only thing that helps with these is having played long enough to get more pets, and secondarily get more growth on them. Getting UPC early will help get more growth over time, but if you only just finished the UPC series then going into this would have no advantage.

In terms of rewards as it only gains you the early pet levels that don't take as much xp to complete anyway, if you actually level them up to a reasonable value the difference is going to be quite small, so the main advantage is going to be in challenges with limited clones, and even then for things like UBC/PGC where you don't get direct stat boosts from pet multipliers it is probably only going to really help with the campaigns in the first rebirth (before you have stats enough to level up the pets to the target values reasonably quickly, and have more clones to play with anyway)

Reward: Reduce the growth of P Baal stats by up to 50%
Cap: 50
Prerequisite challenges: UPC, CBC
Beneficial challenge rewards: GMMC, 1kC, GSC, NDC, AAC, GPC, NRDC, PMC, CPC, TMC, MCC, PBC

Essential/Required for: UGC, 1CCC, LCC, PGC
Helpful for: PBC, NRDC, USC

Estimated duration (early game): 96 hours
Estimated duration (mid game): 40 hours
Estimated duration (late game): 24 hours

Comments: While these challenges are very nice to have outside of challenges, and some of the benefits (extra GP from more P Baals killed, higher DivGen base conversion rate, earlier unlock of the P Baal pets) indirectly feed back into making other challenges easier, they are a very long challenge series to complete, especially given they require high activity - might rebirths most of the way, lack of clones for pet training (exacerbated by the regular rebirths), disabling most of the TBS boosts making frequent trips to that tab necessary (or if skipped, more rebirths and longer time to complete each challenge).

This seems to lead to a very wide range of when they are done - some people suggest doing them pretty early to get them out of the way before you get used to all the "comforts" GP can buy, while others leave them almost to last.

Completing UPC first seems worthwhile - the extra rewards from GP campaigns will be a big boost to progress in the early rebirths, getting creation speed boosts faster, and then also boosting build speed earlier, and then finally picking up 1 or 2 extra CC to make (re)building clones for killing UBs for the energy/crystals much faster and easier, as well as building your clone cap to 99999 much quicker.

The other big boost is the CBCs reward - unlike DRCs, these still work in a UBC, which will make progress a bit easier generally (via boosting stats, etc.), but especially by extending the full set of might unleash to 55 seconds instead of just 5, which is fairly frequently going to allow you to clear an extra god per rebirth, significantly reducing the number of rebirths needed per challenge, and of course the time taken.

MCC and TMC will also help as they double the speed you will accumulate CP and TM during the challenge, increasing things like creation speed/build speed passively, as well as boosting your stats.

Another non-challenge benefit of leaving them to later will be the GP gains from dungeons, by leaving it long enough you have good enough pets to get to the various GP events that can be found, you can significantly increase your GP earnings (although it can be highly variable - Clam in Mountain D3 might get you 200+ GP for a single 6 hour run, or nothing).

Reward: Increases the GP reward for killing a P Baal by up to 100% (200% after UCC20 complete), increases rebirth multiplier cap of monument upgrades by 100% (200% after UCC20 complete), also adds 50% to Black Hole rebirth multiplier if all 25 completed
Cap: 25 (50 after UCC20 complete)
Prerequisite challenges: DRC
Beneficial challenge rewards: UPC, GSC, BHC, NDC, AAC, CBC, NRC, UBC, UCC, TMC, 1kBHC, UBV2C, NDMC

Essential/Required for: 1CCC
Helpful for: UBC(?), GPC, USC, PGC

Estimated duration (early game): 24 to 240+ hours (1st to 25th)
Estimated duration (mid game): 5 to 24 hours (1st to 25th)
Estimated duration (late game): 4 to 14 hours (1st to 25th), then 14 to 36 hours (26th to 50th)

Comments: A challenge series that could easily be started relatively early on, given the first ones are basically not much more than DRCs with a rebirth cap of 4 - although if done too early even the very first ones will be virtual UACs. Early in the game the amount of P Baal kills are fairly few anyway, so a few done for a low chance of a bonus GP here and there probably isn't worth the trouble.

In the latter part of the early game and mid-game you kill P Baals significantly more frequently (for example during a CPC with it's 3-4h rebirth cycle you could well be killing 20 or 30 P Baals each time, which if you have done all this challenge series is an extra 5-10GP per hour. It also makes any time outside challenges generate more GP.

However in terms of directly benefitting other challenges it is fairly limited - the GP benefits won't directly help, so there is only the rebirth multipliers part of the reward, which requires both that you build enough monuments that you would exceed the base cap, and that increasing your rebirth multipliers will help finish the challenge more quickly - while this could help DRC-likes with their might rebirth to climb an extra god per rebirth occasionally, the ones you might consider doing after completing these, for example NDCs, you won't tend to be building enough upgrades even in the later rebirths of each.

The last couple of rebirths of CBCs/UBCs might build enough upgrades to benefit depending on your progress/strategy, although with CBCs even if it does that only indirectly helps anyway, but in most cases challenges that let you build lots of monuments/upgrades are either very early challenges like DRCs, or doing so doesn't directly help you win the challenge.

One particular note is UBCs - if doing these relatively early then having done the UBC series will fairly substantially reduce the time taken for the later challenges of this series particularly (to the point it could be considered a requirement/pre-requisite). However if left until towards the end game, so nearly all of the other of the listed helpful challenges are done, and with lots more base power (pets, pet growth, might boost, crystal power, clones, etc.) then UBCs will have a much more limited impacted - by the late game you should probably be able to do 5 might rebirths and reach P Baal 25 even with only 1 UBC, so all having the rest of the UBCs would do at that point is allow you shorten a couple of the early rebirths to 1 hour instead of might rebirths or something like that.

Once all 20 UCCs have been done a further 25 of these are unlocked, meaning needing to go all the way to P Baal 50 - at that point having the UBCs done will really be essential.

Reward: Increase the rewards of UUC, PMC, NDC, 1kC, DRC, CBC by 10 each (if all 20 done, increase rewards of GSC, AAC, CPC by 5 each and unlocks 5 more NRCs and 25 more PBCs), benefits to OC beyond 20
Cap: 9999
Prerequisite challenges: UUC, PMC, NDC, 1kC, DRC, CBC, GSC, AAC, CPC
Beneficial challenge rewards: Virtually everything else

Essential/Required for: 1CCC
Helpful for: Almost everything (except you will have virtually done them all to unlock this series)

Estimated duration (early game): Not available
Estimated duration (mid game): Not available
Estimated duration (late game): 2 to 240+ hours (1st to 20th)

Comments: Given the rewards nature of additively increasing the rewards of other challenges, it isn't going to be critical for anything, but due to the increase in nine different challenge series rewards it is going to help almost everything else somewhat - that is if you do them before you have completed everything else first. Of course most of the challenge series are explicitly in-game prerequisites, and even for the ones that aren't, there isn't going to be a huge advantage to doing the UCCs first anyway.

So this is pretty much guaranteed to be one of the last few challenge series to do and, well, it was designed for that purpose basically, so I guess that is to be expected.

Reward: Increase the Black Hole multipliers by up to 0.2% per level gained in new Black Hole+ might training, increase in Black Hole passive GP gain by up to 100%
Cap: 20
Prerequisite challenges: UPC, UUC
Beneficial challenge rewards: NDC, PMC, NRC

Essential/Required for: None
Helpful for: TMC, PBC, NDMC, GPC, UGC, LCC, USC

Estimated duration (early game): Not available
Estimated duration (mid game): 48 hours (note unlike most estimates in this guide, this assumes use of consumables)
Estimated duration (late game): 30 hours (note unlike most estimates in this guide, this assumes use of consumables)

Comments: While doing just one of these to unlock the new might training category helps get a few more levels during a DMC and slightly speeds up TMCs, completing this challenge series doesn't usually have much in the way of directly benefits to other challenges - levelling up the might training and the extra boost to rebirth multipliers are beneficial during a P Baal climb, but few challenges are really going to benefit from this (especially given how late this challenge series almost has to done due to the build speed requirement).

The only real exception is probably the second half of the PBC series (after UCCs are done) - the extra rebirth multiplier boost should speed these up moderately.

In terms of challenges that are worth having first, it is mostly ones that boost divinity because those 1000 clones (or slightly less that are free to assign) aren't going to be building up your DivGen very far. Once you have enough divinity then it is just a matter of build speed (so CPC might have helped a bit, if you had enough clones to build a crystal...or kill an UB, and if the tab wasn't locked if I remember correctly), so no other challenges really matter at that point - except indirectly UPC and it helping accumulated some extra Chakra Pills during past item campaigns.

Reward: Up to 100% bonus to UBV2 multiplier boost, after 10 complete will auto kill UBV2s at 250*tier Physical Attack+
Cap: 10
Prerequisite challenges: DRC, 1kC
Beneficial challenge rewards: CBC

Essential/Required for: PMC
Helpful for: GSC, NDC, NRC, PBC, CBC, UGC, LCC

Estimated duration (early game): Not available
Estimated duration (mid game): 12-24 hours
Estimated duration (late game): 3 hours

Comments: Essentially for this challenge, particularly the later ones, you need to raise Physical Defense+ well over 750 so you can actually survive hits from the later V2s, and Physical Attack+ needs to be equally a priority to do reasonable damage, the rest comes down to experimenting with loops that work well, so it is only really the challenges that help with Might levelling that help this challenge.

The reward boosts your stats so helps with all the challenges that revolve around killing Baal to complete each challenge, although many of them are probably going to be completed long before you are killing all V2s easily enough to do harder versions of them - NRC and the second set of PBCs are the main possibilities you might do after this.

As noted in the comments by Ibn Battuta the increase in planet multiplier is very helpful for PMCs, so it is probably a good idea to do these before starting that challenge series.

Reward:Up to 20% cheaper creation buying, after 21 monuments build time 10% less
Cap: 21
Prerequisite challenges: None
Beneficial challenge rewards: DRC, 1kC, UUC, GSC, BHC, NDC, AAC, CBC, 1kBHC, MMC, TMC

Essential/Required for: None
Helpful for: MMC, NRC, PBC, UGC, USC

Estimated duration (early game): Not available/practical
Estimated duration (mid game): ?
Estimated duration (late game): 1 minute to 8 hours (1st to 21st)

Comments: Note the times for this tend to be very exponential because the rate at which you build basic materials grows but also the amount of inputs drops (so for example if you have creation stat to make 4xContinents and 3x Weather, then you need to produce 3000 continents to make about 6000 weather, you only need to queue 2000 weather which need about 1000 continents so you queue only 250 of them. The only thing that tends to slow things down is when the creations you need have a large amount of air/water/stone or whatever.

This also implies that if you expect them to be relatively slow, it can be worth ensuring you are at high level of multiplier/P Baals killed when moving to this challenge, as the higher your creation stat is, the faster it will go.

Note that as the 22nd challenge doesn't give a game beneficial bonus I don't include it in the summary stats above.

Reward:SpaceDim will level up to 40% faster, with all 20 the caps increase to 2500
Cap: 20
Prerequisite challenges: None
Beneficial challenge rewards: UGC

Essential/Required for: None
Helpful for: Nearly all

Estimated duration (early game): Not available/realistic
Estimated duration (mid game): 1 hour to 10 days (1st to 20th)
Estimated duration (late game): 3 minutes to 12 hours (1st to 20th)

Comments: Note that this challenge series is entirely dependent on how many light clones you have, so because they have been added recently "late" game will vary a bit - future players might find this a relatively earlier challenge in the series than long term players that have only gained the ability to gain light clones after playing for a few years. I have used 100k clones for a mid game player and 2m for late game, but this is an easy one to calculate accurately (for the ones you can unlock the P Baal in question early in the rebirth anyway).

Due to all the different bonuses the rewards will benefit almost all the challenge series a bit, although ones that run long will tend to benefit more than quick rebirth style challenges.

Reward:RTI will level up to 20% faster
Cap: 20
Prerequisite challenges: None
Beneficial challenge rewards: None

Essential/Required for: None
Helpful for: Nearly all

Estimated duration (early game): Not available
Estimated duration (mid game): 1 hour to 1 days (1st to 20th)
Estimated duration (late game): 30 minutes to 12 hours (1st to 20th)

Comments: Note that this challenge series is heavily dependent on how many shadow clones you have, and can shift into the RTI tab - for the final challenges in the series I was putting around 300m clones into the tab for almost the entire rebirth.

The benefits of this tab are kind of spread around, so accumulating levels faster in it will benefit a bunch of challenges a bit but nothing exceptional for any of them.

Reward:Shadow Clones created up to 50% faster
Cap: 25
Prerequisite challenges: UBC, PBC, UCC
Beneficial challenge rewards: NDC, AAC, MMC

Essential/Required for: None
Helpful for: CBC?, might rebirth or faster challenges

Estimated duration (early game): 2 days to 2 weeks (1st to 25th)
Estimated duration (mid game): 12 hours to 2 days (1st to 25th)
Estimated duration (late game): 4 to 12 hours (1st to 25th)

Comments: Given to do these relatively quickly you need to kill as many P Baals as to generate GP to buy instant clones in the final rebirth, probably at a rate of 30 minutes per rebirth, although earlier in the game it might be better slowing down to might rebirths after a while - this of course is about 3 times as long, but if it means a lot more P Baals and if you are earning 3 GP for each, i.e. have completed all PBCs, it might work out better if otherwise you mostly would end up killing the original set of gods for 0/1 GP each or only a few P Baals.

Faster clone production is going to help a lot of challenges a little bit, and be more helpful for ones with lots of rebirths, and could potentially be very useful for CBCs, depending on whether the production when at 1 CC rounds up, down or you get 3 every 2 ticks.

Reward: Increase the growth of Pets by up to 50%
Cap: 25
Prerequisite challenges: UPC, CBC, UBC
Beneficial challenge rewards: MMC, 1kC, GSC, NDC, AAC, GPC, NRDC, PMC, CPC, TMC, MCC, PBC

Essential/Required for: None
Helpful for: Double Rebirth Challenges (if any left by the time you do this one)

Estimated duration (early game): Not Available
Estimated duration (mid game): 40 hours to 144 hours (1st to 25th)
Estimated duration (late game): 12 hours to 72 hours (1st to 25th)

Comments: Essentially the same as UBC in terms of which challenges are useful (although individual PGC rules may affect this) but running on past Baal further each time

Completing UPC first seems worthwhile - the extra rewards from GP campaigns will be a big boost to progress in the early rebirths, more GP for clones (unlike UBC you won't just rely on the "free" 99999 - I often had 500k or more during the later ones), getting creation speed boosts faster, and then also boosting build speed earlier, and then sometimes picking up some extra CC to make (re)building clones for killing UBs much faster and easier (or directly using 3GP to buy 100k instantly instead).

Another non-challenge benefit of leaving them to later will be the GP gains from dungeons as well, by leaving it long enough you have good enough pets to get to the various GP events that can be found, you can significantly increase your GP earnings (although it can be highly variable - Clam in Mountain D3 might get you 200+ GP for a single 6 hour run, or nothing).

The other big boost is the CBCs reward - unlike DRCs, these still work in a PGC, which will make progress a bit easier generally (via boosting stats, etc.), but especially by extending the full set of might unleash to 55 seconds instead of just 5, which is fairly frequently going to allow you to clear an extra god per rebirth, significantly reducing the number of rebirths needed per challenge, and of course the time taken.

MCC and TMC will also help as they double the speed you will accumulate CP and TM during the challenge, increasing things like creation speed/build speed passively, as well as boosting your stats.

In terms of the benefits for other challenges, it is something around an extra 100% or so onto your stats (as you will get more levels in the same time training against clones) from the pet bonus, which will help any challenges that need you to climb gods as fast as possible - i.e. most of the double rebirth challenges.

Reward:Monsters give up to 300% more divinity, extra Monster added (to double it again presumably)
Cap: 20
Prerequisite challenges: None
Beneficial challenge rewards: Many (all that help kill more gods per rebirth)

Essential/Required for: None
Helpful for: UBC, maybe 1kC, 1CCC and to a lesser extent other double rebirth challenges up until DivGen is unlocked

Estimated duration (early game): 12 hours to 3 days (1st to 20th)
Estimated duration (mid game): 2 hours to 12 hours (1st to 20th)
Estimated duration (late game): 1 to 2 hours (1st to 20th)

Comments: Note that this challenge series is heavily dependent on how quickly you can get to the end of the Monster tab (or to a few P Baals in basically), and then as the series continues it gets only slightly harder - to about P Baal 10 for the final version (just over 1e80hp), so potentially this might be a reasonable challenge series to do in the mid game - a few quick rebirths then slow down to might rebirths once the multipliers stop growing much in 15-30 min rebirths.

Contrary to that though I am unsure what significant benefits there are from this challenge bonus - normally monster divinity is just the starting point for getting enough to build the DivGen, and then after that it makes no difference because it doesn't increase as your DivGen gets improved (and even the base DivGen tends to massively eclipse it).

The only possibilities I can see are challenges where the DivGen is locked or unattainable, but most things that lock it will be NoDiv challenges. Possibly it will be a little useful in things like 1kC and OCCC to get you to the DivGen faster during "crippled" challenge modes like this. In theory it could be useful for any double rebirth (or GP reset) challenge for players that find those challenges slow enough a significant amount of time is spent before unlocking the DivGen, however I think it is quite likely grinding through the MQC slowly during the early/mid game will not give enough benefit to these challenges to offset doing them so early (as the benefit is only pre-DivGen, whereas most of the other challenges give benefits both before and after DivGen unlocks), and the more of such series are done before this, the less benefit from doing it at all (and it has no real effect on "normal" play or normal rebirth based challenges).

Reward: Increases the BP reward for killing a P Baal by up to 50%
Cap: 20
Prerequisite challenges: DRC, GSC, BHC, UBC, 1kC
Beneficial challenge rewards: UPC, NDC, AAC, CBC, NRC, UCC, TMC, 1kBHC, UBV2C, NDMC

Essential/Required for: LCC
Helpful for: SDC (indirectly), UBV4C (indirectly)

Estimated duration (early game): N/A
Estimated duration (mid game): 8 hours to 10 days (1st to 20th)
Estimated duration (late game): 4 to 72 hours (1st to 20th)

Comments: A challenge series that could be started in the mid game given the first ones are basically not much more than an extended DRC to P Baal 11 and so on - however the 20% increased gap per god per challenge done rapidly adds up to a massive increase in the latter P Baals power levels, which is exercerbated by doing far fewer gods. The last few gods of each of the later challenge could easily turn into days long rebirths just to get one more god down until in the very late game, and even then expect to have to extend to 9-12 hour rebirths or more just to advance a god or two at best during the end stages of the final challenges of the series.

The benefit for most challenges is also somewhat indirect - you will earn Light Clones faster mostly (or in theory more of the other things BP can be spent on, but most of those are of little relevance by the time you are likely to be able to do this challenge), so eventually things like the Space Dim Challenge and UBV4 Challenges will be a bit faster, although completing this series just before trying either of those won't help as it takes time for the benefit to accumulate, and many other types of challenges interrupt light clone production anyway, so given how slow the later challenges can be it probably isn't worth completing these first - doing the easier ones in this series might be worthwhile, given it isn't a series with a especially big final bonus for completion.

As a guide, although it will probably be misleading due to the fewer God/Statistic multipliers accumulated, on the 20th version of this challenge P Baal V29 has a power level of 2.74e147, and V30 has 6.87e149 (so should end up about P Baal 54 once completing it), but in terms of needing half day region rebirths to advance one god, it felt more like something in the P Baal 105-115 sort of range for me currently.

Reward:Get up to 25% bonus light clones when purchasing them (bonus doesn't count against price increase)
Cap: 25
Prerequisite challenges: UBC, UGC, DRC, 1kC, GSC, AAC
Beneficial challenge rewards: BHC, NDC, MMC, TMC, CBC, NRC, PMC, CPC, 1kBHC, UBV2C, NDMC

Essential/Required for: None
Helpful for: UBV4C (indirectly), minor boosts to most (via levelling Space Dim faster due to more LCs)

Estimated duration (early game): 12 hours to impossible (1st to 25th)
Estimated duration (mid game): 2 hours to 2 weeks (1st to 25th)
Estimated duration (late game): 1 to 48 hours (1st to 25th)

Comments: Because of the need to raise the average per rebirth, the requirements for the later challenges in this series tend to grow exponentially the earlier you attempt to do it, meaning there are lots of challenges that help you push more Gods per rebirth that help increase the amount of BP you are earning per rebirth. You can of course also rebirth much slower to get more gods per rebirth and do them earlier but that will add up to quite an increase in the challenge duration, as that will need multiple long rebirths for the higher targets.

There is also the trade off between amount of LC resets you use during the challenge and how quickly you can do them - for me 6 rebirths of 3-6 hours including one longer one into the PB80s resetting at 1500 cost about 7-8 resets for the final few, or you can save a reset or so by resetting at 2000 requiring a couple more rebirths (and longer ones). Resetting at 1000 conversely would cost a couple more resets but save one rebirth.

As well as the general boost to the Space Dim, this will also help kill UBV4s faster in the long run due to the number of LCs acting as a multiplier for your attack/defense and healing.

Reward:Get up to 25% bonus on Rune Patch armour that boosts craft speed and quality, or boosts team damage in dungeons with all 25 done
Cap: 25
Prerequisite challenges: 1kC, GSC, BHC, NDC
Beneficial challenge rewards: UPC, NRC, PMC, UBC, PBC, 1kBHC, NDMC

Essential/Required for: None
Helpful for: None

Estimated duration (early game): ?
Estimated duration (mid game): 2 hours to 48 hours (1st to 25th)
Estimated duration (late game): 1 to 24 hours (1st to 25th)

Comments: The wide range of stats that boost your score in this, and the way in which they multiply together suggests doing this quite late, this is particularly true for things that boost the divinity generator (as then you create more universes and turn them into Black Hole upgrades scoring twice), but also lots of clones (for divinity, Black Holes, building unleash power, RTI), lots of evolved pets (and more pets in general), etc.

Reward: Decreases the time needed for UBV4 fights by 1 minute each
Cap: 5
Prerequisite challenges: 1kC
Beneficial challenge rewards: SDC

Essential/Required for: None
Helpful for: None

Estimated duration (early game): N/A
Estimated duration (mid game): N/A
Estimated duration (late game): 18 to 120 hours (1st to 5th)

Comments: The first few of these are really not much different to a normal UBV4 clear, the fourth took me about 50% longer than normal without changing from normal practises in terms of levelling up particular areas, but for the final challenge you will need a lot more in the particular areas that boost V4 fights - Physical HP+ (until hitting the cap of 100 hp/shadow clone), Mystic Regen + (mine reached 23000 and wasn't even healing half the 60-90m clones it was killing each round), and Recursive Memory in the Space Dim area to help level those faster, and also Dimension Beamer (at 7000 I was almost taking the shield down in 6 rounds).

So in terms of challenges not much helps directly, and I can't see anything it really helps with in terms of other challenges so definitely seems like one to leave until very late on, although the first two or three you might do once you can comfortably beat ItRtG V4 just to get a large chunk of the benefit while just needing to do a couple of moderate sized rebirths. The more time your dungeon pets have to power up and get better equipment, the easier this will be, so procrastinate all you like here.

Reward:Overflow points that can be spent on various bonuses
Cap: 9999
Prerequisite challenges: None
Beneficial challenge rewards: Nearly all

Essential/Required for: None
Helpful for: Nearly all

Estimated duration (early game): 6 hours
Estimated duration (mid game): 6 hours
Estimated duration (late game): 6 hours

Comments: Hard one to advise on, generally this will just be a challenge you do when other challenges are done or too slow to do yet, but there might be value in getting enough points to buy some of the more key purchases or cheap early levels in preference to some other more marginal challenge series.

Reward: Increases Worker DivGen fill speed, the bonus from overcapped number of workers, and increases the amount of Divinity gained from killing UBs
Cap: 25
Prerequisite challenges: ?
Beneficial challenge rewards: ?

Essential/Required for: ?
Helpful for: ?

Estimated duration (early game): Not practical
Estimated duration (mid game): 4 to 96 hours (1st to 25th)
Estimated duration (late game): 0.1 to 24 hours (1st to 25th)

Comments: (lots of DivGen, build speed ++, RTI, Might)

Reward: Increases time bonus by up to 100% (after up to 100 minutes)
Cap: 26
Prerequisite challenges: ?
Beneficial challenge rewards: ?

Essential/Required for: ?
Helpful for: ?

Estimated duration (early game): Not practical
Estimated duration (mid game): 2 hours to 96 hours (1st to 26th)
Estimated duration (late game): 0.1 hours to 18 hours (1st to 26th)

Comments: By the later editions of this, the amount of god multipliers missed, the lack of materials for monuments or crystals means you end up just doing two rebirths of medium length and then longer one, as you barely get any benefit from rebirthing any more than this.

As well as the mentioned challenges others that boost monuments and crystals will help for the early challenges in this series, but they are all pretty fast anyway (similar to the original GSCs) until you lose monument upgrades, and then the DivGen (and with that crystals effectively), and then even the pittance of bonus from monuments without upgrades disappears as well, leaving a mix of raw power from pets/crystal power/total might and splatting UBs for as long as it takes to reach the finish line, with each of the last challenges requiring making it a further lost 4x bonus from one less god that appears.

Reward: Increase of up to 100% physical and mystic from training
Cap: 20
Prerequisite challenges: ?
Beneficial challenge rewards: ?

Essential/Required for: ?
Helpful for: ?

Estimated duration (early game): 24 hours
Estimated duration (mid game): 6 hours
Estimated duration (late game): 2 hours

Comments: (no physical/mystic, no might, PB20 target)

Reward: Up to 100% boost of Total Might, final gives 10% Might level up speed boost
Cap: 20
Prerequisite challenges: 1kC
Beneficial challenge rewards: UCC40

Essential/Required for: None
Helpful for: ?

Estimated duration (early game): ?
Estimated duration (mid game): ?
Estimated duration (late game): 1.5 hours to 3 hrs (1st to 20th)

Comments: (clones)

Reward: First unlocks Multiverse Boost, then up to 100% speed increase for Multiverse Boost
Cap: 21
Prerequisite challenges: ?
Beneficial challenge rewards: ?

Essential/Required for: ?
Helpful for: ?

Estimated duration (early game): ?
Estimated duration (mid game): ?
Estimated duration (late game): 30 minutes to 6 hrs (1st to 21st)

Comments: There are basically two stages to this challenge - building up the DivGen and then building a bunch of universes, and then flipping most of the clones over to building Multiverses, so amount of clones is a key here, as well as build speed and other divinity boosts which will allow you to spend less time on that phase of the challenge, and then clones and creation speed to actually build the multiverses.

Reward: Up to 25% build speed boost
Cap: 25
Prerequisite challenges: ?
Beneficial challenge rewards: ?

Essential/Required for: ?
Helpful for: EMC, ?

Estimated duration (early game): ?
Estimated duration (mid game): ?
Estimated duration (late game): 2 hours to 12 hours (1st to 25th)

Comments: (DivGen to fuel creations, RTI helps passively a little, Crystals can be key but lack of clones, just free Might helps kill UBs a little easier but don't tend to put any clones there)

Reward: Creation count boosted by up to 50%
Cap: 26
Prerequisite challenges: ?
Beneficial challenge rewards: ?

Essential/Required for: ?
Helpful for: ?

Estimated duration (early game): N/A
Estimated duration (mid game): N/A
Estimated duration (late game): 5 seconds to 12 hrs (1st to 26th)

Comments: This is pretty much entirely based on creation count and creation speed, and I think it is unlikely to be possible to complete all of them until you can overcap universes (i.e. get it below 0.03s to build, although using both Godly liquids will make a huge different and is probably required for the later entries of this series), as over 100k per tick will be disappearing of everything.

Players not in the late game might benefit from doing some of the earlier ones as they are much easier, Ocean is where things step up a bit, then Weather jumps up further, then Moon/Planet/Earthlike, Sun is a bit of a break (you have to make a LOT of light, but only that and enough Air/Water to make crystals to boost your creation count), and then the last 3 need a lot of prebuilding of the basics, then prebuild as many of the intermediate creations as you can without running down the basics you still need for the later creations, all to save a few ticks of switching between creations to build the last few steps - given each extra creation you have to build in the final attempt is going to cost you 100k of each creation already done, so can easily cause everything to break down as it gets stuck trying to build one of them but they are being eaten faster than you can create once the base creation stock you have has been eaten through.

Cheesy as it may be save scumming I think is essential for this challenge given you can eat through hours of Light creations you have built up or whatever in less than a second and have everything that was created disappear before the end of that second because you were just short of the target, putting you back to the start (apart from a higher creation count).

Reward: Monuments boost each others effects with a special bonus, final one adds an overcapping effect for monument boosts at 10% of pre-cap effectiveness
Cap: 25
Prerequisite challenges: ?
Beneficial challenge rewards: ?

Essential/Required for: ?
Helpful for: ?

Estimated duration (early game): N/A
Estimated duration (mid game): N/A
Estimated duration (late game): 6 hours to 3 days (1st to 25th)

Comments: (lots of DivGen, build speed ++, RTI, Might)

Reward: Unlocks Super DivGen then raises it effectiveness up to 100%
Cap: 20
Prerequisite challenges: ?
Beneficial challenge rewards: ?

Essential/Required for: None
Helpful for: None

Estimated duration (early game): ?
Estimated duration (mid game): ?
Estimated duration (late game): 10 hours to 9 days (1st to 20th)

Comments: Just need lots of clones and build speed, and you will probably want lots of pills on hand to speed things up further. I don't think this really helps with any challenges apart from those in the specific situation it is designed to address (very late game players who are offline a lot getting reduced level ups on the DivGen some of the time)

Reward: Unlocks up to 50 ghost SpaceDim levels
Cap: 25
Prerequisite challenges: ?
Beneficial challenge rewards: ?

Essential/Required for: None
Helpful for: None

Estimated duration (early game): ?
Estimated duration (mid game): ?
Estimated duration (late game): 3 minutes to 3 hours (1st to 25th)

Comments: Just need lots of light clones, sped up a bit by high RTI levels and overflow points spent on the Space Dim speed. It isn't likely to have a significant benefit for any other challenges by the time you are likely to do it however.

Reward: Reduces unleash cooldown by up to 60 minutes
Cap: 10
Prerequisite challenges: ?
Beneficial challenge rewards: ?

Essential/Required for: None
Helpful for: None

Estimated duration (early game): ?
Estimated duration (mid game): ?
Estimated duration (late game): 1.5 hours to 12 hours (1st to 10th)

Comments: Just need lots of clones and might speed boosts.

Reward: Increase upgrade chance of crystals by up to 10%
Cap: 25
Prerequisite challenges: ?
Beneficial challenge rewards: ?

Essential/Required for: None
Helpful for: None

Estimated duration (early game): ?
Estimated duration (mid game): ?
Estimated duration (late game): 3 hours to 3 days (1st to 25th)

Comments: Assuming you can reach the requisite PBaal during an NRC of whatever length it turns out, the main aspect to doing these efficiently is stacking your daily resets as much as feasible without messing up other things (primarily the quest reset for the tavern) too much. This way once you have a reasonable crystal factory giving you quicker L1 crystal build up you can then sacrifice every 6-12 hours instead of doing them evenly at 24 hour intervals. It is likely the last crystal power related challenge you will do (unless/until new ones get added), so it is only really a background boost rather than something to particularly prioritise.

Reward: Increase gain from god power purchases Build Speed/Creating Speed by up to 100%
Cap: 25
Prerequisite challenges: ?
Beneficial challenge rewards: ?

Essential/Required for: ?
Helpful for: ?

Estimated duration (early game): ?
Estimated duration (mid game): ?
Estimated duration (late game): 1 hour to 9 hours (1st to 25th)

Comments: The benefit of this challenge depends on how much you spend on BS/CS, given over time you gain crystal power passively, if the amount of BS/CS you get from that is low then doubling it will not make a huge difference, however if you spend a lot of GP on them it will be a big boost.

As you need 250m clones before you can do the challenge it isn't an early game challenge, but as soon as you hit that mark you can probably do these reasonably efficiently, and the boost to BS and CS will be useful in a fair range of other challenges, although having a decent CC score to do the creations in as few cycles as possible will keep the time down.

Reward: Increase amount of LC bought before the price increases from 500 to up to 800
Cap: 30
Prerequisite challenges: LCC, ?
Beneficial challenge rewards: ?

Essential/Required for: ?
Helpful for: ?

Estimated duration (early game): ?
Estimated duration (mid game): ?
Estimated duration (late game): 9 hours to 42 hours (1st to 30th)

Comments: Indirectly this will benefit SDC and SDAC over time as you will accumulate more LCs than without this challenge done and UB4C will slowly get easier with a higher LC count to multiply up your other, but apart from that the benefits will be fairly diffuse, i.e. the various benefits from levelling up the various SpaceDim elements slightly faster (in theory eventually approaching 30% faster, minus the impact of capping them out and the scaling costs of each level).