Who Should I mega evolve for my team Salamence or Tyranitar or Gengar. The rest of my team is Greninja, Heatran, and of course Jolteon But don't worry to much about them right now I'm looking for who would be the strongest individually with the mega stone. I am taking movest suggestions but please only base your answers on the movesets below. So overall in an answer for me to give the BA I would like to see base stats type matchups and movesets all considered in your response.
Ev's-252 .Atk, 252 .Def, 4 Sp.Def
Ev's-252 .Atk, 252 .Spd, 4 Sp.D
Ability: Levitate(Let's go Oras)
Ev's-252 Sp.Atk, 252 .Spd, 4 Sp.D
If you need additional info just let me know in the comments.