Where do you find gardevoir?

Answer 1

Gardevoir alone is never found in the wild.

However, its preceding evolution, Kirlia, can be found in Diamond and Pearl on Routes 203 and 204 (south), and in Platinum on Route 209 using the Pokeradar and on Route 212 (north).

In addition, Kirlia's preceeding evolution, and the original species that can eventually evolve into gardevoir is Ralts. Ralts can be found many places throughout the games:

Ruby, Sapphire, and Emerald: Route 102

Pokemon XD: Snagged from Cipher Peon Feldas in the ONBS Station Top

Diamond and Pearl: Routes 203 and 204 (south)

Platinum: Routes 208 and 209

HeartGold and SoulSilver: Route 34

Another option would be to find a friend who has a Gardevoir (or any of the others in Gardevoir's evolution line [such as Ralts, Kirlia, or Gallade]) and ask for the friend to either trade you his or her Gardevoir or breed it with a Ditto to give you a level 1 or 5 (depending on which game your friend is playing) Ralts.

Good Luck!