Mine evolved at level 30

I chose gastly, but for the ledgendary dogs they know roar and run away again

If you r training in the mt. Silver area, on your what to find red, etc, I found so many it eventually became annoying. I train up there so much 'cause I evolve my little pokemon by switching out with my mewtwo. They evolve with good stats that way. Hope this helps!-kira