Question

I have a eevee at level 20 and it knows: Sand-Attack, Tackle, Growl and Helping Hand.
Quiet nature. Hates to lose. Ability: Adaptability.So at what level should I evolve my eevee into leafon?

Comments

Well, it depends on what moves you want for your Leafeon; if you wanted a Baton Pass Eevee team then you need your Eevee to learn Baton Pass at Level 33 (36 in BW). Otherwise, you can evolve your Eevee as soon as you want if you won't use any of Eevee's level up moves. Go here: http://bulbapedia.bulbagarden.net/wiki/Eevee_(Pok%C3%A9mon) for Eevee's moveset and see if any of its moves are useful for what you're planning to do with your Leafeon.

Answer 1

Evolve it as soon as possible, because Eevee doesn't learn any moves after level 20 that Leafeon would want.

Source: Experience