@LPF and I were idly discussing Legendary Holster and how to play it out of each faction, so here is my attempt at doing it out of First Peoples. The structure is fairly standard tight-structure Holster, A-2-3 with a few cuts to make room for Legendary Holster and Doomsday Supply. It shoots fairly well, and can deal with attrition fights thanks to the 8 copies of 1 cost Spirit sidekicks in the deck. This deck should hold its own against other shootout-oriented decks due to being able to tussle on their level and use the acing effects of Legendary Holster and Shotgun to wear down your opponent.
Your choices for Holster holders that are also Shamans (to use the Sidekick Spirits) are basically Geronimo, Matilda Loomis, Sarah Meoquanee, or Joseph Dusty Hill. I went with Matilda because she has influence and no upkeep, and Geronimo because he is a natural stud. I could see a version of this deck that uses Sarah Meoquanee instead and loosens the structure up to include 4s, but that would be a pretty significant change.
The clubs are a pretty standard indecisive split, normally I would move toward more consolidated numbers but I haven't played the deck enough to know what exactly it needs. It has a decent amount of cheatin' punishment and shootout interaction, but no forced callouts. If you are worried about passive decks in your playgroup you should probably not play this deck, or at a minimum you should include some amount of forced callouts and/or other win conditions such as Establishin' Who's in Charge or Hustings for some on-value examples. ...It's who you know is also a possibility when combined with the outfit ability.