I am in a rush, but PokémonDB says you can find Eevee in Celadon City, but after combing Celadon, I couldn’t find it. Can someone give me the precise location and instructions on how to get there?
You can’t get the gift Eevee there like you can other Kanto games. However, if you go left into the Pokémon Road, you can find an Eevee there after a few minutes if you’re lucky :)
This is just a minor mistake in PokémonDB, you can't get gift Eevee anymore.
Like KRLW said there are Eevees in Route 17 (the cycling road).