Attack and maybe MP pots so his refresh gives him a bit more each turn. You don't need to give them to him before awakening, though - probably better not to, since I think you can give more pots after awakening than before.
His limit's not very good (mild defense debuff with physical damage), no reason to spend limit pots on him.
Equipment wise, long term blade mastery + katana, short term give him a regular sword (e.g. Enhancer) in one slot so his passive works. He's pretty easy to get to the point where he's pretty useful.
He'll be nice in the arena once everyone has crazy ailment characters, since he naturally resists petrify, blind, confuse. If you give him an accessory to protect against sleep he can probably power through just about anything.