Gem uses

I've gotten my 5th builder hut quite awhile ago in my coc career. I've also been recieving $10 itunes gift card (these gift cards are from app bounty) and immediately bought gems. What should I do with these gems? Right now I have 4,447. I'll still be recieving itunes gift cards in the future from the app aswell

If you're a good farmer, I'd gem lab time upgrades and boost barracks and spell factory when raiding,
btw I've tried using appbounty I have 2839 points, can't get to 6k