Stats are simple- ALL DEX...some say a little vit or int, but in a power build you will want ALL DEX.
Now my view on the gunner is dishing the MOST DAMAGE and killing quickly without regard to HP.
(Remember, no skill build is the best, the best skill build would be the one that matches your playing style)
Now- I made a few mistakes in this---first off, wind force is RARELY used and if you find a use for it, you'll notice it's damage is poor. Dont put more than 1 point on it...worst mistake I made was put 5 points on wind force and 1 point on hammer, they BOTH suck....
First off, save till 3-shot, then put 5 points on there, save till sharp eye, by now you should have a good amount of SP saved up, MAX OUT SHARP EYE ASAP (you will notice a HUGE damage increase at this point). This is now your choice, I tried maxing Gatling gun but the damage BARELY goes up for the SP cost, I RECOMMEND you max out 3-shot and in your final levels put the minimum 5 on quick shot, and 3 on Gatling (requirement for heavy armor). Quick shot is again, a useless skill, though even with 3 point Gatling is still a usable skill (3-shot is slightly weaker but has quicker cool down). Save remaining SP for Gunner. The 6 points I messed up should have been saved for gunner skills. (wind force and hammer)
Now when you become a gunner, your fighting style will be fitted with skills even further. (meaning the best skill build varies from person to person)
As I said, my build is "PURE DAMAGE" mixed with AOE.
I don't favor close courters (hence why I'm a gunner in the first place) so I dont use wild bombard. Crasher is lvl 35 and is a pretty strong AOE (MP expensive though, roughly 100mp per use, faster cool down than galating) well its really good for getting out of corners. Wild shot is useless in my opinion, it simply shoots in 2 directions doing crap damage to the monsters in front and behind you, NOT WORTH GETTING. Bazooka...requires level 55 so its a while before you get it.
My build is--- put minimum requirements for Crasher, then save till lvl 35, then put all on crasher. This part is all what YOU want: Max out crasher first, or add skill points between crasher and Heavy armor (heavy armor is good but u can substitute it for the haste/speed skill instead), continue this until both are maxed or until level 55 in which of course would be max bazooka, the supposed strongest gunner skill. Now I have not gotten to the level for bazooka but I have tested every gunner skill up to my level so I have confidence in my current skill build.