I want to offer a rufflet for a vullaby on the GTS (desent trade right?) well I go to offer a rufflet and when it asks for what I want the is no vullaby option! why?
Because vullaby is not in your pokedex you can only request pokemon in your pokedex
Vullaby is not there probably because you haven't met one,to look for a Pokemon on the GTS,you must have it in the pokedex(Not necessarily caught just seen).