All-Out Attacker (Gastly) (M) @ Life Orb  
Ability: Levitate  
Level: 5  
EVs: 36 Def / 196 SpA / 76 SpD / 196 Spe  
Timid Nature  
IVs: 0 Atk  
- Sludge Bomb / Sludge Wave
- Shadow Ball / Sludge Wave / Thunderbolt
- Psychic / Thunderbolt / Dazzling Gleam / Substitute
- Protect / Substitute
 
Set Details : Sludge Bomb and Sludge Wave are two powerful Poison STABs, especially when boosted by Life Orb, which can hit a good portion of the metagame for at least neutral damage. Sludge Wave has the advantage of hitting both opposing Pokemon at once and bypassing redirection moves like Rage Powder and Follow Me, at the detriment of hitting its teammate if the latter isn't immune to it and doesn't Protect. Gastly can also choose to run both Poison-type moves, to be able to choose between spread damage and more damage to a single target. Alternatively, Shadow Ball is a good secondary STAB move that has awesome neutral coverage, notably hitting very hard Magnemite which is immune to Poison, Ground-types like Onix and Mudbray, and Gothita. Thunderbolt is a good coverage alternative, especially with Sludge Wave, since it allows Gastly to still be able to hit Rufflet and Vullaby very hard without having Sludge Bomb, while also threatening Water types like Squirtle and Omanyte. Finally, other coverage options include Psychic, which has a good chance of OHKOing regular fast Mienfoo and deal more damage to Foongus and Koffing, and Dazzling Gleam, which is another spread move that can cover Scraggy and can deal solid damage to both Mienfoo and Vullaby. Substitute can be used to take advantage of opposing Pokemon switching or using Protect, making Gastly far more difficult to threaten out. Protect is a staple of Doubles in general, and can be used to stall out opposing speed control and gives turns for teammates to deal with Pokemon that threaten Gastly or to provide support. Finally, Icy Wind could be an option over a coverage move to give Gastly some support capability.
The used spread maximizes Gastly's Special Attack and Speed, and a Life Orb is used to allow Gastly to hit as hard as possible. With Gastly's frailty, most Pokemon can threaten Gastly with their attacks, so redirection users like Foongus and Squirtle, and Fake Out users like Mienfoo and Scraggy are good partners. The latter two can also threaten Pawniard, which is the only Pokemon that can shrug off any of Gastly's attacks. Finally, Gastly appreciates speed control from Tailwind users like Rufflet and Vullaby, and from Pokemon that can deny Trick Room or opposing Tailwind like Taunt Mienfoo and Roar Mudbray. Finally, if running Sludge Wave, teammates that are immune to it like Pawniard and Magnemite and Mudbray, who can get a Stamina boost from it, are useful teammates.