Note: If this Pokemon has the Levitate ability, it will be immune to all Ground attacks.
Description: The goal of this build is so once they've taken down your Substitute, Disable ruins the move that likely had the best chance of getting Gengar out of the way. Substitute is to give you a buffer against Paralysis, Pursuit users, and make Disable far easier to pull off. It also helps ruin mono-attacking walls (such as Ferrothorn, Blissey, Chansey, etc) and offensive Pokemon that only have one or two coverage moves.
Shadow Ball and Focus Blast give Gengar perfect neutral coverage (with Shadow Ball getting a nice STAB) making it all the easier to either cripple an opponent by removing it's only method of Gengar annihilation or KOing them with a powerful attack that is going to hit them for either normally effective or super effective damage.
This is a good moveset for gengar (Pokemon #94) with the levitate ability/trait, a Timid nature, and equipped with Leftovers submitted by Venustoise. For use in competitive Pokemon battles featuring an Export option and breeding guide.