Frey, Clause, Maria and Aisha are all good characters.

Gau (tanking will be less than clause, but can do a lot of CC bar damage in raids/world boss)

Lakrak (a CCer, so competing with maria, less hard cc but usually more damage when doing it)

Kualah (offensive support healer, CC immunity while channeling heal rather than through, has stun capabilities, and can give atk speed/crit buff to team)

Epis (magical assissin, wouldn't bother getting her unless you have her UW, and even then you should probably wait until later)

Selene (physical dps, so much like epis probably ignore for now since you have aisha and you're getting nyx)

Miruru (another heavy CCer, so probably ignore since you have maria)

Lorraine (another CCer, but this one is more world boss/raid aimed like gau, so potentially useful)

Dimael (dps/cc hbrid, so probably ignore)

Demia (tanker, works fairly similarly to clause, so could just stick with him for now)

Reina (should probably avoid her, as there are better options for most of her roles)

Overally, getting Kaulah would probably be a good choice (though most of the time you'll still use frey in story mode). Or just keep it for the future (in which case you might end up using it on gau/lorraine when you get to world boss).