Hello everyone

Jagged Alliance 3 is a challenging game with a surprising amount of depth, but also a punishing experience.

I've put together a brief, spoiler free list of tips I really wish I knew when I was just starting, in particular the first tip is a game changer and the sole motivator of me creating this guide because it feels like a core mechanic that I didn't stumble across until many hours in.

Tip one;
The most valuable tip here – you can create your own mercenary, who does not cost you ANY upkeep!
You can assign the mercs stats and perks in any way you like, to create a fighter, support character sneaky assassin or hybrid of your choice!
But the most important aspect is that this mercenary never costs you any upkeep, you pay the initial cost and that's it, saving you, quite literally, hundreds of thousands to millions of dollars compared to any other mercenary.
Early game, atleast until you acquire your first mine, money is a serious issue as you have zero income other than what you scavenge, while your mercs wages eat away at your funds.

To get this mercenary, you need to navigate to the in-game browser.
F2 key for short, or from the map/satellite screen, click command, then browser.
From the browser, click on the I.M.P Web tab and take the P.E.T test.
Pay the one off fee of $7000, take the test and your latest hire will be made available.
Personally, I'd highly recommend including this custom made character as part of your initial squad. Your bank account will be greatful.

Tip 2;
Pressing left alt key toggles on and off visual indicators which highlight lootable containers/corpses and things of interest.

Tip3;
There a few valuables that the game tells you to sell, but actually have other uses, which I generally discovered too late.
:Tiny diamonds – you can sell them at any time for $500, but that is a poor use of them.
There is a merchant that trades information for diamonds, and who also offers boxes of random (but extremely high quality) loot for them.
There is a character who will purchase tiny diamonds from you for $600, or $700 each after a successful conversation check.
:Bags of Grand Chien currency can be traded to an unusual merchant for rare crafting materials and other random goods including but not limited to explosives and parts.
:Ancient artificats can be given to a story character in exchange for loyalty and she will give you several milita soldiers to assign to any of your owned provinces.

Tip 4;
Each world map location/square can and should be entered and explored. Even if enemies are not present and the location has no significance for quests or merchants, you can find loot, hackable objects, intel, scavengeble parts and medicinal herbs, all of which are extremely important.
Edit: This also includes river sectors. I didn't know at first that even tiles in the middle of a river could still be explored. (be careful in river sectors or those with large bodies of water that are not seawater as chances are there are several crocodiles which will attack your party. Crocodiles are slow, but they are armoured, have a very large health pool, huge melee damage and will get free attacks against any merc in melee range who tries to move away or perform any action while being in melee range)

Tip 5;
Every occupied sector has a stash that you can use for storage. From the map screen, opening the inventory will display the stash of the sector that your squad is standing in.
Otherwise, on the bottom right of the map screen, there is a series of buttons to toggle what you see on the map, the 4th from the top is to highlight all sector stashes so you can see what items are in which stash.
Keep in mind, that stashed gear can only be retrieved if a squad is in that sector.

Tip 6;
Ammo and explosives can be crafted if your squad contains a merc with explosives skills and you are at a location with a workshop. Most city centers have a workshop, otherwise look for tiles that have a marker that looks like a house with a wrench icon.

Tip 7;
Ads for A.I.M Gold will start popping up. This $20,000 service does nothing but allow you the privilege to hire legendary mercenaries.
Be aware that these mercs cost more upkeep than a single early-mid game diamond mine can keep up with, let alone a squad.
Edit: AIM Gold is eventually given to the player for free, deep into the campaign. -Thanks andrew.a.drozd

Tip 8;
Time resting can heal wounds (remaining idle on the world map, neither moving or participating in an operation), a process that is sped up significantly if the mercenaries are performing the R&R operation inside towns. This is a very slow method of healing, but if you are out of increasingly scarce meds it is an option.

Tip 9;
The conversation perks such as psycho, negotiation, scoundrel ect are very handy, and several quests are locked without them.

Tip 10;
Establishing militia squads in conquered provinces does pay off long term.
Aside from securing your conquered territory, as they repel attackers any loot (including from killed defenders) is put into the sector stash providing another way to gain ammunition, weapons and scrap.

Tip 11;
Repeatedly talk to the unnamed people you meet in the world!
Villagers, miners, guards ect, as they can give your squad information about quests, provide quests or give intel about neighbouring sectors.
While this can be time consuming, it can be very beneficial. I need to do a lot more research to discern if the villger tip offs are connected to the loyalty of the nearest settlement.
Thanks to Motorola for this fantastic tip!

Tip 12;
Check if items have the 'combine' function in your inventory.
Its a rarely used function as it seems like most crafting was moved to operations.
One of the best 'combine' crafting options is to combine wire cutters with pipe bombs. This destroys the pipe bomb, but provides ever valuable gunpowder.

Tip 13;
This one is vital!
As you get further into the game, you will start encountering items that are booby trapped with either mechanical or explosive traps, but the game does a poor job of differentiating, as the icon is the same and I was going mad trying to discern a way to tell them apart.
Thanks to Czupak in the comments, we can all know better now.
If the tool tip over the trap lists 'disarm' the trap, then it needs an explosive expert to defuse.
If the tool tip lists disable the trap, it needs a mechanical expert to defuse.

I did intend for this to be a brief list of tips, so I'll stop here.

I wish I knew these things when I started playing, hopefully they help you!


PS: Thankyou to those who have commented below with really helpful additional tips, I'm positive they have helped a lot of people.