>>53337824Reroll until you get a couple meta characters.
Always save at least 36 600 gems before you even think of rolling. Using that amount lets you choose a unit for free. For example, using 30k and stopping would be a waste. Might as well spend a few more and get the banner's featured unit.
By using 5 star Power Ups (PUs), you can raise a unit from 5 Stars to 6 Stars, with an additional EX upgrade. The EX upgrade gives your Sync Move (a Limit Break) a new feature. Focus on 6EXing a few good Support units first, as they tend to be more useful.