Umbreon really isn’t a stat-lowerer. It’s built more to tank, and is therefore pretty bad in-game. I highly recommend Espeon instead, just saying. Anyway, a good Umbreon set is:
Umbreon @ Doesn’t Matter, it’s in-game, but Lefties if available. EDIT: Ooops I guess Black Glasses
Nature: Again, it’s in-game so it doesn’t matter much
Feint Attack, I guess.
So really, Espeon preforms much, much better in-game as opposed to Umbreon. If you want Umbreon though, I recommend the above set.