You can get adjustable cam gears from Jim Wolf, but you should get cams before you get cam gears... and if you get JWT cams then the JWT cam gears are almost useless because the JWT cams have been tuned for optimum performance without needing to be adjusted.
I'd say the only reason you should be getting cam gears is if you have a turbo system and you want to try advancing or retarding your cams. Even then it's not really necessary.
NA, you're not going to gain any power from cam gears. You shift the powerband around, but you're not really going to gain any peak HP. Running with turbos, you can use the cam gears to reduce overlap and reduce the chances of reversion; but that's about it.