Electivire's cause of life is to be a Hardcore Sweeper.
And then a normal sweeper EV Spread for Electivire would be:
252 Atk
252 Spe
4 HP
or...
200 Atk
200 Spe
110 HP
Both of these spreads work well.
You can try out a fast staller Electivire but I doubt the success:
252 Spe
252 HP
4 Def/SpD