I would go for Elia, he's awesome for me as an inside forward on the left wing, but that's in the French League 1, dunno if he'll be that good in EPL, he tore apart OM deffence recently in of my games, with Azpilicueta on the RB position. I had Mata on a previous save wasnt really impressed, but maybe I just didnt use him in the right position, and I have no experience with Navas.
Edit: Go BIG on the striker transfer, Aguero really would be perfect.