Once your level and skill tree is maxed out (you can really ignore the energy tree), you want to focus on your moves. Do dailies (unfortunately Big Band has the most annoying daily to complete) until you get a move with at least 2 from attack %, defense %, HP%, meter gain or crit rate (crit damage is generally fine as long as you have decent crit rate). If 3 of those are on the move, its considered very good. You want to upgrade these moves, the max being level 15. This costs an exorbitant amount of money so generally its better to level moves evenly rather than one at a time.