With Kerry already reduced twice and leveled and no need for extra duelists, I'd probably skip investing a lot into Emilia. Unless you're in a rush for xp on a particular unit, you should always aim to get more bonus xp by combining same class if you still need levels. As for 2-2 or 1-3 on spirit usage that depends on your number of spare spirits and space constraints, only you can answer that. Typically I do 2-2 for farm units myself though.