A very good Gengar Moveset
Hypnosis
Dream Eater
Curse
Nightmare
Hypnosis simply because of Dream Eater and NIghtmare
and use Curse first Dream Eater heals half of the damage u dealt and nightmare inflicts about 1/5-1/6 hp
I have used this on the Dragon type leader and it did pretty well til i died at her last pokemon.
If you need Nightmare i can give you a level 1 Gastly with it.