Before we start, are you aware of the rules of actions needed to reload guns?
Warpriest counts his class levels as his BAB for qualifying for feats. Grab Vital Strike (Warpriest gets a bonus feat at 3rd level, or your sixth level if you take 3 gunslinger).
Standard Action > Vital Strike with Gun
Move Action > Reload Gun.
No i was not Aware as I though it was like a regular range weapon.
You need a free hand in order to reload a gun. If you are dual-wielding pistols you do not have a free hand and cannot reload.
If you want to dual-wield pistols on a spellcaster gunslinger, your best option is the Juggler Bard archetype with the Mysterious Stranger Gunslinger archetype. The Juggler gives you the ability to literally juggle items so you can use the two firearms and still have a free hand to reload, and Mysterious Stranger makes grit charisma-based while giving you a cha-to-damage option that synergizes well with the bard.
With my Gunslinger/Warpriest, the shiniest bits were Sacred Weapon (Warpriest 4) and Gun Training (Gunslinger 5). Since Warpriest 4 gets you several other useful things like 2nd-level Cleric spells, I went Gunslinger 1 (to get the whole chassis, proficiencies, Gunsmithing, etc.), then Warpriest to 4, taking Pistol as my free Weapon Focus so I could buff my gun. Now I'm working my way through Gunslinger again. Not sure if I'll go to 5 or 7 (Targeting is kinda nice when you realize it bypasses CMD and has no saving throw).
Divine Favor will probably be your go-to buff for swift-casting with Fervor. You might be tempted by Abundant Ammunition, but remember that it targets an object, which means you can't swift-cast it with Fervor, so at least early on when you're only firing once a round it probably won't be worth spending a Standard action on (and at later levels you'll probably have to cash and carrying capacity that you won't need it anyway). Same with Magic Weapon and anything that targets an object or weapon.
As for reloading, both the Rapid Reload feat and Alchemical Cartridges reduce the reload time by a step, so with a one-handed firearm it takes a free action to reload if you have both.
Remember also that both reloading and firing provoke Attacks of Opportunity, so something with Combat Reflexes can ruin your day if you don't take the right precautions. In my case, I went with the Gun Tank archetype and often end up in melee, so I'm working my way toward the Deft Shootist deed, which prevents both from provoking (Point Blank Master only affects shooting, not reloading). If you don't get drafted into being the front-line, you probably don't need to worry about that too much.
Remember you hit TOUCH AC within 40ft with a Rifle, making it incredibly easy to hit.
"Reloading" bows is a free action.
Reloading a light or hand crossbow is a move action.
Reloading a heavy crossbow or one handed fire arm is a standard action.
Reloading a two handed fire arm is a full round action.
Muskeeter brings muskets down to as-if one handed fire arms. Alchemical Cartridges and Rapid Reload bring you to free action reloading.
If you don't want to use the Vital Strike, look at the Arsenal Chaplain Warpriest. You give up some Sacred Damage (your gun will be doing more until past 15th Warpriest level anyways) for some base damage. You get Weapon Training which qualifies you for the Advance Weapon Training feat in order to grab advance weapon training from the Fighter.
As for Gold. You need to give your weapon a +1 before you can add special abilities. Remember that Alchemical Cartridges make your misfire rate 1 higher (1-2 rather than just 1). If you grab Lucky you can reroll misfires for a grit point or grab Reliable which lowers your misfire chance by 1. (to 0 if you don't use Alchemical Cartrides). That will cost you 8000g total.
You have 6300g left after weapon and armor. I suggest a Headband of Wisdom (+2 wisdom) or a Belt of Dex (+2 dex) for 4000g. Then either increase your AC with a ring of protection for 2000g (+1 deflection AC, works to touch and flat footed AC) or a Cloak of Resistance (+1 to all saves) for 1000g and upgrade your armor (+1 armor AC, doesn't help with touch AC) for 1000g.
Spend the last 300g on ammo and mundane supplies.
Your required feats are Point Blank Shot (required for most ranged feats), Rapid Reload, and Precise Shot. Your last feat is up between Rapid Shot (-2 to attack rolls, but you get one more attack) or Deadly Aim (-1 to hit, +2 to damage, increases after every 4 BAB, so right now you have -2 to hit, +4 to damage).
Important distinction between Musket and Rifle, Rifle goes to free-action reloads with just Rapid Reload, no Musket Master necessary (all advanced firearms are free-action with RR, regardless of type).
Because of wording, Rapid Reload has zero effect on Advance Firearms. Rapid Reload says two handed fire arms are reduced down to a standard action, not that it reduces the reloading a step.
Has there been a ruling on whether the revised RR text vs the Firearms rules takes precedence?
From the SRD -
Advanced Firearms: Advanced firearms are chamber-loaded. It is a move action to load a one-handed or two-handed advanced firearm to its full capacity. The Rapid Reload feat reduces this to a free action.
Muskets aren't advanced firearms and most GMs don't use advanced firearms.