I don't see how Dragonite's and Eevee's connect, unless you're referring to CP. In that case, farm the Eevee's. Vaporeon is currently the second strongest Pokemon in the game (right behind Snorlax) because of Water Gun.
As for where to farm them, I would suggest the park in New York. I got quite a lot of Eevee's there.
Latitude 40.720160
Longitude -73.879816