First, I'm only interested in rules-as-written supported tactics and strategies. No creative interpretations, no GM adjudications necessary. The only exception to this is that my GM has preemptively given me the okay to use the Gunsmithing feat to craft revolvers for 2000 gp and 4 days downtime.
I'm pretty adamant about using revolvers as opposed to multi-barreled one-handed early firearms. Rapid Reload only reduces reloading to a move action for early firearms, which means reloading during a fight is even worse. The revolvers at least have a capacity of six shots versus the double pistol's two, so I can make a full-round attack with my full BAB and an off-hand attack and still have ammo left over. When you add in the fact that early firearms carry the risk of exploding due to misfires and the worse range, they just aren't a viable long-term solution. Paper cartridges also increase the chances of a misfire, which increases the chance of an explosion (and a misfire is an automatic miss with my attack). Furthermore, you have to reload each barrel of a multi-barrel early firearm separately. I think my GM would have a problem with me using 4+ free actions to reload in a single round during a full-round attack, which is what would be necessary to make a full-round attack at 16+ BAB and an off-hand attack from TWF without being out of ammo when my next turn came up.
Multiclassing is fair game, and I can use anything on the D20 Pathfinder SRD. I suspect that this will lead to a dip in a class that provides sneak attack. Answers that make this suggestion should include the best levels at which to take said dips, and should compare the value of these dips to the value of True Grit (see below).
Play begins at first level and stats are obtained via 30 point buy. Prioritize DEX and WIS, dump STR and CHA. I'm thinking something like 7/18/16/14/18/5 (STR/DEX/CON/INT/WIS/CHA) after racial modifiers but I'm open to alternatives since this array leaves me with 1 remaining point that I can't spend on any of my scores. I'm also currently planning on putting 4 out of my 5 stat increases into DEX; I'll probably start with Leather Armor because it has no armor check penalty, I'll have a small carrying capacity due to low STR, and it carries a max DEX bonus of +6 which perfectly matches my eventual minimum 22 DEX score.
I'm primarily interested in feat progression. Answers suggesting dual-wielding and TWF should explain how best to reload in the heat of battle without holstering one of my guns, since even with Rapid Reload making reloading an advanced one-handed firearm a Free Action, reloading still requires one hand being free. I'm also interested in optimal Prestige Class choices.
Obviously, assuming the game lasts long enough for me to get True Grit at 20th level (and I decide not to multiclass), my first choice will be Up Close and Deadly to get the additional 5d6 damage to all my attacks for free but I'm interested in hearing suggestions for the second choice.
Skill-wise, assume that I will put at least 1 point into Craft (Alchemy) and keep Perception maxed out. I'm open to suggestion for maximization on the rest of my skill points but I don't think they will contribute much if at all to my damage output except for helping to craft better guns/ammo, or investing in Stealth for use with sneak attacks if multiclassing.
For traits, use the default restrictions:
There are a few rules governing trait selection. To begin with, your GM controls how many bonus traits a PC begins with; the default assumption is two traits. When selecting traits, you may not select more than one from the same list of traits (the four basic traits each count as a separate list for this purpose). Certain types of traits may have additional requirements, as detailed in the section above.
Remember also that traits are intended to model events that were formative in your character’s development, either events from before he became an adventurer, or (in the case of additional traits gained via the Additional Traits feat) ones that happened while adventuring. Even if your character becomes a hermit and abandons society, he’ll still retain his legacy of growing up an aristocrat if he took the relevant social trait. The one exception to this is religion traits—since these traits require continued faith in a specific deity, your character can indeed lose the benefits of these traits if he switches religions. In this case, consult your GM for your options. She may simply rule that your character loses that trait, or she might allow him to pick a new religion trait tied to his new deity. Another option is that if your character abandons a religion, he loses the associated religion trait until he gains an experience level, at which point he may replace a lost religion trait with a basic faith trait.
Assume that my chosen deity is the dwarven deity Droskar.