The Start

My recommended starting party (for details read further below) : Start tournament over until you get summoners with Extrovert perk. Start with 3 summoners (or archers, works similary), than add a rhino as next unit for tanking. then add a pyromancer (or skeleton mage) and a priestess, maybe an early hookbot. Add additional units from these categorys. You may want to add 1 or 2 archers for sniping pyromancers and enemy archers, which are the only really scary enemies. Maybe one cryomancer or alternatively (and even better) a skeleton mage for slowing down enemy movement. And you may want to add a necromancer, which will ressurect fallen enemies to fight on your side. And you can try a marauder (max out int first!) to run as fast as you can to the strongest pyro or archer and stunlock him. Even better seems to be the hookbot, which pulls archers and pyros to them, before they can cast/shoot. Very effective, when you can kill them quickly after that (e.g. with 3 summoners standing behind the hookbot, which hit the pulled enemies with shadow bolts and send their minions on them after that).
But all this will work only until ...

You die!

You will die. Absolutely. No chance. Enemies get very quickly absurdly strong. I had Bosses with level 1000+ and "normal" enemies with 300+. Nobody can handle this. You can skip some fights in the end, do the easier ones and then perish. Nothing to do about this.

You can start the tournament over and over, until you get one or two of the units you wanna get in the end. If you really go for reaching rank 100 or better you should absolutely do this. Rinse and repeat for the right starting units with the good perks (like Extrovert and Energy vampire).

But what are the best units?

TANK
Best tank in my opinion is the rhino. He can pull all enemies to it (taunt) and doesn't need much stats (except some agility for cooldown cap). This is so strong because he even taunts the fast units and even the units with camouflage which are chasing for your ranged units. Too good.
Very easy to level: You can invest nearly all points into health. With a healer he is nearly unkillable.
Perk: Firm as a rock (can't be knocked down). So he can get to the ranged units.

HEAL
Only one option:The priestess with her heal and her wonderful shield. Put some points in agility (or do it later with items and invest all points into health and stamina). If you reach the cooldown cap with a lot of agility you will also need very much stamina.

DD
The archers are really strong and will carry you through the first fights - and further ...
But late in the game, you will encounter level 200 pyromancers which kill all your archers in a single shot. Keep that in mind.
Easy to level: All points in agility, until you reach accuracy cap. 3 or 4 points in intelligence for cooldown cap. After that you can mix points into life, stamina and agility (agility gives more damage and less execution time). When you reach the cap for execution time invest your last points (before you die) into strength/life/stamina.
Perk: Energy vampire, takes away 5% stamina from enemies. If you have two archers with that perk, bosses are a cakewalk, cause they are out of stamina and frozen in place. And when they are level 1000+? No problem with that perk!

The pyromancers are good too. They do some significantly damage and throw enemies back. You can use items to scale that burning damage with your archers and your pyromancers.
Not so easy to level: Put some points into strength first, to maximize the radius of your fireball. After that you need some points in agility for cooldown and execution cap. And you need more points for intelligence to scale the damage and some points into life and stamina. Even strength scales the initial damage of the fireball further. Full of compromises ...
Perk: Energy vampire, takes away 5% stamina from enemies AND / OR Extrovert.

The summoner is really strong in two ways: His minions will cover the battlefield and help against ranged damage. They dont do that much damage, even at level 30+. Really strong is his shadow bolt. Both abilities scale with intelligence, so he is easy to level: Mix points between agility (cooldown and execution cap) and mostly intelligence (or pure int and use items for agility). This unit really needs the perk Extrovert.

The purifier seems not to scale very well in early game. You need lots of agility to make his damaging ability even work. Maybe something for further testing. Don't like it so far.

The berserker seems to be not so strong. The problem with him is, that he can't get to his targets, cause he is hinderd and knocked back all the time. When he is free to move, he deals great damage and knocks down. But most of the time he behaves in a way you will not like.
Leveling: If you want the knockdown, give some points into intelligence. But he can use it only every 5 seconds.The long axe attack scales very well with strength (Extrovert perk!) and with agility, which you need for execution cap. Don't like him so far.

The Spearman comes with Power in numbers, which is quite strong. The only useful ability is his spear attack. Easy to level: a few opoints into int for cooldown, the rest is pure agility. Has the same problem as other not ranged DDs with getting to the enemies. Not so strong.

The Explosion-bot deals some nice damage when he explodes himself, if he can get to the right targets. Thats again the problem, cause he has problems to get to those pyros and archers. Best combination seems to be the necromancer, cause he can resurrect him to explode again.

The Brigand has a nice spear attack, which deals good damage with an ok cooldown. The net which freezes enemies isnt that good, cause it only hinders one enemy. For this purpose a Skeleton mage or Cryomancer is better. Not so easy to level: You need a lot of agility for accuracy and execution time. A few points into int for cooldown, rest in strength, which scales damage best.

SUPPORT
Best support unit seems to be the Hookbot. He pulls enemy archers and pyros to him. If you can position for example three summoners behind him, they will kill the pulled enemy quickly. When the enemy arrives, he is directly hit by three shadow bolts and after that three minions go after him. For me the only possibility to keep strong ranged enemies under control.
The hookbot is easy to level: all points into agility for cooldowns.

The necromancer can be strong in a team which kills enemies quickly and with a single important perk: Extrovert. You should really take this, cause only with this perk you can reach more than 300 int. He will raise from death a killed own unit or any enemy unit you killed. The level of that unit depends on his intelligence. So you want to have it as high as possible.
Easy to level: some points into agility to reach the cooldown and execution cap, intelligence mostly. But if you really hold him up to the light, the summoner seams to be stronger. He can produce minions and he has a damaging ability which does 500, 1000 and later more than 2000 damage per shot. The necromancer just stands there and waits.

The shaman is quite nice, cause his totems heal and do fire damage. But they don't heal really good and they don't do significant damage. Try it out, they are relatively easy to level:
You again need the perk Extrovert to scale your intelligence and with that the level of your totems. You will want to reach around 37 agility to reach cooldown and execution cap. And you need an enormous amount of stamina to keep casting those totems. And you need a lot of life, cause these hazardeurs go melee. Sick and not very clever. If they woud stay behind everything would be fine.

The cryomancer and the skeleton mage don't seem to scale very good into midgame. Their freeze against fast moving units which chase your damage dealers is nice, but we already have a tank for that issue. You really have to bring those nasty pyromancers and archers down asap and for that they don't help. Their damage it not worth mentioning. Later in the game, when the enemies get level 300+ they start to blitz around the battlefield very quickly. Then a cryomancer comes in handy. Recommendation: One Skeleton mage from midgame on, cause he freezes enemies AND gives a shield (high cooldown).

The marauder can be good to engage and lock down the scariest enemies: pyromancers and archers. You will give him int first so that his stun ability is on cooldown nearly all the time. Later you will need some movement speed (25+) to get to those foes quickly before they can cast a single time. One cast from a level 250 pyromancer will annihilate your complete army. I would choose one with high int and stamina naturally.

TO BE CONTINUED ...
Leave comments with your experience plz
As you already noticed: I'm not a native speaker.

Perks are really important for diving deep into tournament. They are a reason to start tournament over and over to get the good ones. And you really should refresh the gladiator shop often to get the best.

There are two perks, which are really outstanding:

Extrovert is so good, because you can scale one attribute really high. This is especially good for summoning units of all kind, cause their summons scale with this attribute (int).

Energy vampire is really good against bosses. You want to have it on fast firing ranged DDs like the archer. It reduces the stamina of the enemy really fast. When they are out of stamina, they dont act anymore and you can kill them easily (even if they are level 1000+).

Some other perks are good too:

Fast Wits is good combined with one of the other good perks early on. When you buy units later in the game they wont level more than 1 or 2 times which doesnt make a difference. But taken early on you will get levels faster and build an overall stronger character.