Gengar/Dusknoir

Gengar's Creep Show attack is extremely powerful, and both Dusknoirs helps to maximize its effect. Dark Invitation is great for adding a few extra damage counters and another Pokémon, while Sinister Hand can guarantee a knock out every turn, with the effects of Old Cemetery and Radiant Charjabug. Marnie and N are great ways to refresh your opponents hand to use dark invitation, while simultaneously refreshing your own hand! I considered Wicke, but at many points you don't have much of a hand,

Gengar's Creep Show attack is extremely powerful, and both Dusknoirs helps to maximize its effect. Dark Invitation is great for adding a few extra damage counters and another Pokémon, while Sinister Hand can guarantee a knock out every turn, with the effects of Old Cemetery and Radiant Charjabug. Marnie and N are great ways to refresh your opponents hand to use dark invitation, while simultaneously refreshing your own hand! I considered Wicke, but at many points you don't have much of a hand, so N and Marnie are better. These should be used mostly in the mid-late game though, as any stage 2 deck needs to keep its hand. I'd recommend attempting to get a Noivern V attacking with boomburst first turn in order to get early damage spread, especially since most decks play Battle VIP Pass for speedy openings. You could also add Life Dew and a Spell Tag to justify an inclusion of Arven, but Skyla gets the job done. I found that in previous iterations without noivern as a starter/consistency tool, we immediately lose. We also use valuable deck space and stadium space on Old Cemetery, when Dimension Valley is far more useful in reducing energy count and getting rid of that pesky Parallel City.

Opening: for the opening, you should use Skyla, Switch, Fog Crystal, and Mysterious Treasure to get Noivern V in the active spot and attacking first turn. Most openings have a combination that allows you to get Noivern V active, or at least a chance of that.

Mid-Late Game:  you should get a Gengar attacking and Dusknoirs ready to support with their abilities. Dimension Valley is also crucial to allow Gengar to attack efficiently, so prioritize putting it in play, but wait for after the fist turn so it doesn't get bumped out, unless you are playing N or Marnie in your opening. Boss is also important to taking multiple prizes with one attack and preserving damage counters. Arezu is also a good mid game card to evolve quickly. 

I find that Gengar is a really fun deck to play with and I hope you do too!