The game is pretty good but they really need to fine tune the AP regen/ requirements for battles + coin drops..
I am pretty much stuck with getting stronger because most of my AP gets used up on story or daily missions to get elemental fragments to unlock higher levels. And when I finally unlock them I cant even properly level up the girls because it cost coins... seriously why using xp books or unlocking higher level cost coins and shit ton at that. Regular instances provide pretty much nothing in terms of xp considering the amount you need to level up.
And when I finally have some leftover coins to level up my gear I cant because I lack the materials because I dont have AP to do bunch of runs in instances...It is like never-ending circle...