Jolteons in training. Who's 1st in class?

I've been saving my Eevees but I definitely think now is the time to get the best of em in LL and OGPP lineups and rest of em to the Professor. I have a Sylveon and 1 Espeon already. Pretty sure my other best 3 or 4 Vees are Jolteon material? So, which of those are the best/recommended jolty boys?

As for any others, let me know if there are any additional ones? Looking for outstanding Espeons [who I'd prioritize evolving ASAP], a decent Vaporeon, and maybe 1 Leafeon if I'm struggling to stay gassed up on LL.