As the title implies.
Any suggestions?
Let me reiterate:
I want to play a Gestalt firearms user geared towards performance combat, making trickshots and mesmerizing the audience with gun twirling.
Any advice?
Gestalt? Gunslinger with mysterious stranger and bard.
Mysterious Stranger is great for Dexterity to damage with your gun and trick shots, but if you want a different bend you could also go with a Dune Drifter Cavalier for a mount, banner, and challenge. There's also the Holy Gun Paladin for that Divine gun Smite. A Picaroon Swashbuckler gets to feint with their gun as part of their full attack and gets a +5 bonus to it at 7th level.
But I'd definitely recommend the Mesmerist as your second class. Half level to Bluff, free feint feats for your gun twirling if you're a Vexing Daredevil, and mental magic frees up your precious reloading hands.
Lots of Bard Archetypes too if you want a Bard. Brazen Deceiver, Daredevil, Fey Prankster, Negotiator, and Street Performer also give half level to Bluff.
Juggler Bard can reload firearms with "hands full". It's kind of cheesy, but how can a gunslinger resist being able to reload dual pistols, or reload a pistol while wielding a sword?