>>539148243
the more you push in the campaign, the more resources you get, and it is much easier to push with meta units
you can just use your favorites, but it will be harder, if not impossible, until you have blue numbers or close to it
with more resources you get more power, which early on more directly affects your special arena (pvp) gem gain every 2 weeks. though if you just actively play every day i think you can chill on diamond 1-3, which nets you 4k per month