Jolteon is too frail for supporting. The only viable Sub set Jolteon can use is this:
-Hidden Power (Ice)
EVs: 252 SAtk/4 SDef/252 Spe
Ability: Volt Absorb
Air Balloon should only be used if you intend to use Jolteon late-game, as it misses out the power that Specs or Life Orb provide if it does opt for Air Balloon.