Brave and faith are the two big core stats. Brave influences physical attack, and faith influences magic. Even though you don't have magic yet, you want your two highest faith characters set as chemists, because the magic classes are accessed though chemist (different jobs have order jobs as prerequisites). You want your highest brave characters as squires, both because they'll be going into physical classes later and because they'll hit harder now. You should be able to view those stats somewhere in your party management in between battles. If you're set up so that your two highest faith characters aren't chemists and your highest brave characters aren't squires, switch that around.

Magic doesn't go off instantaneously, so you can sometimes get to the caster and interrupt them if you are clever with your CT (or use a stone to knock them to a place where they can't hit their target and the spell fizzles). Don't forget to heal if you need it. Buy enough potions to keep you going, and focus fire on the units that are giving you trouble.