Where do you find a Gastly?
You can find them in the Lost tower(South of Solacean town)and In the Old Chateau (In Eterna forest). They are mostly found at night. A Shiny gastly has a blue aura surrounding it. Gastly will evolve at lvl 25 into Haunter. and to obtain Gengar, you must trade. (btw, it is a ghost type meaning that it is useless against normal types.) Good luck trainers!