First of all, lets eliminate Flareon, Jolteon and Vaporeon since you aready have those 3 types in your team.
So the remaining Eeveelutions are:
-Covers for your Flying type's Rock weakness.
-Covers for all of your Fire type's weaknesses.
-Covers for your Electric type's Ground weakness.
Covers for your Fire type's Ground weakness.
Covers for your Fighting type's Flying weakness.
Covers for your Electric type's Ground weakness.
Covers for your Fighting type's Psychic weakness.
Covers for your Normal type's Fighting weakness. (it covers for nothing if Eevee is your Normal type)
I'm guessing the Eevee is the normal.
commented 2 days ago by Scraϝ
So the best Eeveelution for you to have other than Leafeon is Glaceon since it covers for the most weaknesses.