6. Upgrade Your Armory
In addition to gems, you also get points after completing missions or levels in this game. You can use these points to upgrade and improve the units you have.
It is recommended for you to upgrade ranged attack units and defense units. This will be very advantageous because long-range units can knock out enemies faster and strong defenses certainly support every battle.
However, pay attention to always be balanced no matter what formation you use!