I wanna know the best army chassis that has ever been used...Many suggested that for infant(10A,20R), Cavalry(5A,10R), HeavyUnits(3A,7R)...

What is the best one to use?Are there any other setups better than these ones?I've seen many other setups but which one is the best?

u have got the best built.. some call it the pro built.. the 7:3 ratio of range n armor..

Damage units are good to have, especially in even battles.
May I suggest you could try this....
Inf- 17R,3D,10A
Veh- 9R,1D,5A
Tank- 6R,1D,3A

I'm not telling you to use this, but to try it out and not go in battles where the odds are stacked against you.

The pro-build is simply the most flexible build. Its not perfect but it works in the most situations. While other build usually are only preferrable in a set amount of situations they make it difficult to stay good in all situations. Damage builds have proven this by being great in even battles where the enemy and you are roughly even in your percentages.

Example: Your doing 3/0/7 build Armor:Dmg:Rng and your opponent is doing something wacky that works like 6/3/1. There build as wacky as it seems actually works in close battles where the enemy is even in the amount of anti-chasis that they are using. And it really comes down to the point in the game where tactics, activity and strategy are used to decide a round. Pulling together team mates and allies ect.

But for me I usually just do the standard pro-build b/c of its flexibility w/conquers, enemies, ect.

What is more important than your build is your ratio.

If you have 2 enemies and they are inf chasis and tank chasis a good ratio would go as follows. 40:10:60. (Consecutive:Beam:Explosive) For every 10 squads. This concept I think is overlooked more so than the "pro-build" which has become rather famous and standard

There are also other reasons why people prefer range over damage during wars.

One reason is....
Example:
If you use spy to damage units or you nuked an army then don't use damage units to kill the units which are reduced to 1HP that won't work, always use range to kill weak HP units.

Ok....How do i also gain xp's faster!!!??!!?

To gain XP quick you need to kill armies with a lot of armour and very few range or damage. Keep doing this and you will eventually have enough XP for your unit to upgrade.

Nukes can help you with this and spy attacks on colonies that are just starting to build up. Do battle sims to make sure you kill the right amount of units never losing any range

Thanks guys for helping me out!