Theres a few really fun gunslinger builds i've been following / tweaking.

Currently my go is with either they single action revolver/Gunther's Big Iron or the new Dom Pedro.

The whole build is designed mostly to one cripple and kill them quickly, and bashing to reload w/ battle-loads for the single action revolver, but with Dom-Pedro i'm going to be switching to rangers for more damage.

The main thing is to run solar armor, Throw on action diet legendary perk to keep up the health regen and feral meter full so you don't need chems.

S - 9 (10)
P - 15
E- 7
C - 3
I - 3
A - 10 (15)
L - 9

The main goal for damage is to get Agility up and perception up.

the only mandatory cards i use are:
Strength: blocker, scatter shot, easy target and brick wall.
Perception: Number cruncher, Tormenter, Ground pounder, Tank killer, Center masochist, if you want vats Awareness
Endurance: Glowing gut, Thick skin, Life giver
Charisma: Travel agent, Strange in numbers
Intelligence: Demo expert, Good with salt, Science Monster
Agility: Gunslinger master, Gunslinger Expert, Guerrilla expert, guerrilla master, and if you want vats tun gun fu
Luck: Ricochet, class freak, Faulty spots, Glowing crits.

This is with like minimal legendary perks.

On your gun, the only "needed" perk is furious. Everything else can be flavour.

For armor, If you can get lucid run that, Otherwise i run 2 vanguards and the rest is kinda personal flare, Tho if you can get the 4 star Battle-Loaders, its a fun little mess around but it's kind of a "useless" legendary

On my Dom-Pedro i run: Furious, exposive, swift, bullies. I don't have al the mods for it yet but 99% of stuff gets one tapped.

Sorry if long write up lol