>>25052234Vaporeon
Sylveon
Jolteon
Flareon
The last two are up to you in terms of what you can acquire. Leafeon's rock is way the hell at the end of the game in X/Y. Glaceon's is pretty late too. You could go to ORAS and use the stone in Peatalburg woods for Leafeon, but again, Glaceon is at the bottom of a time oriented dungeon right before the second to last gym. If you can get to Petalburg, I'd say grab Leafeon, it is a surprisingly beastly in game mon.
Sylveon basically makes Esepon redundant, but it might not hurt to have another decently quick special attacker. Umbreon is a stally wall, and not great for in game shenanigans.