From Bulbapedia, the community-driven Pokémon encyclopedia.
The Ghost Party Deck is a type deck found in the Gym Heroes Strategy Guide. The deck is classified as one of the advanced decks, containing more rare cards and strategy than other easy-to-build decks.
It's time for a party, and this deck's going to throw one with all your ghostly Pokémon friends. The goal of this deck is to get your Bench loaded up with Gastlys, Haunters, and Gengars. Sabrina's Haunter's Night Spirits attack does a lot of damage for just if you can fill your Bench up this way. Challenge! lets you play more Bills (draw two cards) or fill your Bench—either way, you're coming out ahead here.
If your opponent knocks out some of your Ghost Pokémon, you can get them back with Recycle and Revive. Note that this deck uses four Gastly and four Sabrina's Gastly (you can do this because they count as different Pokémon). You might also think about trying another version of this deck that uses Jigglypuff and Wigglytuff. Wigglytuff's Do the Wave attack also works really well with a Bench full of ghosts.