Birds of a feather; BO offense moxie spam.
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Starting off, classic Gengar. Specs can be swapped out for scarf if you find yourself running into Indeedee Espathra cores and have trouble shutting it down. Trick + Nasty plot really helps vs fatter teams, as you don't have to sacrifice the power of specs in the long run in order to cripple a wall. If you find yourself relying on TFlame's WoW a lot, then hex is another viable option.
TFlame is a great physdef midground given how popular Slither Wing is right now. Punishes spinners like Brableghast, Tsareena and Toedscruel while keeping your own hazards off. Tera Ghost to block spinners who you think are going to ignore flame body repercussions and just go for it.
Quag is spdef midground, hazard setter, and electric immune. Could be swapped out for Gastrodon without spikes if you want a safer team, but I think stacking hazards is much more effective to make use of the moxie users. Walls washtom. Tera Steel for more defensive capabilities should you need it. If you're opting for hex on Gengar, consider tspikes over spikes.
Espathra is just a staple at this point. You know who it is, you know what it does. Moving on.
Banded Honchkrow is something I experimented with back in Gen 7. With a dark tera, banded moxie sucker punch can pretty quickly get out of control, but you sacrifice the possibility of mind games. Life Orb is another viable option here. Slow U-turns are also pretty decent at getting momentum, though Honchkrow's mediocre movepool and lack of a good physical dark STAB is definitely felt.
Opting for DD Moxie Mence since honestly, scarf on mence is pretty mediocre, which is an insane thing to actually read, but Dragon/Flying is not the greatest coverage for a scarf set. Fire fang is an option over DWB to cover Tera steel Hydreigon, though you can just as easily opt for Tera Electric to help cover waters.
Overall, just a fun offense team if you're looking to use Gengar. Generally straightforward to pilot and doesn't require 400 bajillion outplays just to position something, and is pretty forgiving of misplays. Handles a lot of the meta pretty well but still hates stuff like Cloyster, Florges, Webs HO, and that one dude who wont stop running mono choice with Krookodile.