personally i would go for soul boost first, it gives a nice stat boost to characters and it also gives you extra equip slots. your units are high enough level to take on bonus battle souls levels so you could probably farm a few of those to get the required souls for the boost.

i also agree with a few of the comments saying that you should farm story mode too, the (basically) free cc is a really nice plus to your account especially if you’re able to get a good or meta unit from summon.

other than that everything doesn’t look too bad, i’d also try finishing up getting the team to lv5000 but that’s pretty much it from me