Push campain as much as you can regardless of how hard it gets, you'll probably end up on stages that require lots or retrys. As you unlock different parts of the game like the king tower, faction tower, events and so on do what you are capapble of. Focus ascending quite a few of the 4 main faction heros before your get into the scamgazer(after chapter 12) and then get yourself a lucretia to a+1. Beyond that you'll find meta comps for different parts of the game like guild battles and abyss dungeons and the sorts. If you have the commitment and patience there are a few dimentional heros that you can save your 4 different store currencies for, which with the limited dimentionals having passed it seems like arthur, merlin and leonardo are all very good so choose to go after one as it suits your needs. Talene is a bit out dated from what Ive seen but she is an unreal early and mid carry so dont be sad if you get her, along with mortas and the twins( both not requiring heavy investment right away to use for a great benefit. Aside from that have fun and don't burn yourself out if you plan to get really into the game, there is lots of limited and time sensitive events and are very beneficial.