I am working on a Spellscar Drifter for PFS and am looking for general inspiration.
Here's a starting point for you:
Human Spellscar Drifter/Mysterious Stranger
10/16/13/10/10/17
SD1: Gunsmithing, Amateur Gunslinger (deadeye deed), Point-Blank Shot, Precise Shot
SD2:
SD3: Rapid Reload, Deadly Aim, quick clear deed
MS1: Amateur Gunslinger->Extra Grit, +1 Cha, focused aim deed
So at level 4, you're attacking at +6 for 1d8+5 (you'll want to stay away from a two-handed gun as your main weapon, since you can't pick up the deed that lets you reload it as a one-handed weapon), before including Point-Blank Shot. You'll also have 6 grit points to spend on adding Charisma to damage from your dip into Mysterious Stranger.
After that, you can pick up Rapid Shot at level 5, and continue on with whatever ranged combat and grit feats you want.