>>49016816Your three most useful ones there in terms of type advantages will be Lynyrd, Geolady, and SolidSnake.
>NoctowlThanks to its Normal typing, it will be able to negate at least one move from each of his party. If you want something that can hurt him bad, go back to the gate between Goldenrod and 35 and deliver some mail for the guard. You'll get a Psychic-type move for your trouble, which will help immensely.
>GeoladyMagnitude will have both STAB and type advantage against Morty’s Ghosts. She's almost at the evolution point anyway, so expect even heavier hits.
>SolidSnakeBite has type advantage against Ghosts. Just don’t send it out against Gengar, since Dream Eater will absolutely melt its health away.
Your biggest worries outside of that will be all of those Curses and Mimics. If you can keep cool and deal with those, you will be fine.