My main team has generally been:
Lianna
Frederick
Cordelia
Takumi
The Takumi slot is sorta flex. I have a lot of trouble using archers well since they seem to get walled off and take a long time to finish things off, but maybe that'll change as he levels up/gets upgraded. I've been considering a mage, but I'm not really a fan of any of the mage characters. Mostly I just clear maps out by swapping between Lianna, Frederick, and Cordelia who I find all of to be massively entertaining to play as.
I'm also sorta considering swapping out Lianna for Xander, since I value getting around the battlefield quickly and his moveset is great fun as well, but I gotta admit to liking footsoldier swordfighters and I do like Lianna's character.