I would do just a simple 252 SAtk / 252 Spd / 4 SDef. Standard sweeping EVs. It gives you power and speed, and Espeon is meant to be a Calm Mind sweeper so sweeper EVs just make sense. The 4 SDef EVs are just basically thrown in to help boost SDef kinda. xD
However, there is another option. 252 HP in the place of Special Attack is good for having a little extra bulk and gives you an easier time getting up more Calm Minds. Though the power drop can be noticeable sometimes.
Hope I helped! :)