Feed them to themselves (well, to one EVOLVED copy) to improve special/sockets. If you are a new player he is a decent unit.

So I should level up and Evolve one of them (evolved all the way/super evolved?) and then feed the rest to that one? Should I level up the rest of them to max (without evolving or should I evolve them before feeding them?

I'm relatively new I guess. Just finished Whiskey Peak. Hadn't really been doing much Secret Isle stuff and went back and replayed Ace's training grounds with double drop/exp. Crazy.