just to be clear, is that a silver sol Z or just the high rank gunner armor? well, i'd go for the attack up large. you can't have too much attack power when you're a gunner. if you try adding up the elem stat, you'll have to narrow down your weapon of choice just so it could fit with your current elem attack up skill. or if you can still trigger a skill with remaining slots then go for just about anything. try divine protection, that's just 10 points with 5 remaining slots.. IF you already encountered ucamulbas and got his scales to make that divine protect+2 jewel using 1 slot.
---in my opinion, that armor is best suited with a light-bowgun instead. if you want to use a bow, try using load up skill so you can unlock the 4th or final charge on every bow..