My simple advice: Do NOT piggyback! Just remove the scope, etc and attach the camera +lens directly to your mount, assuming you are using a GEM. Piggyback is really only for forkmounted outfits. Any mount will perform far, far better when it carries only a quarter or a tenth of its design capacity. So, if your mount is a GEM, then the question to ask is what dovetail or accessory you need to mount your camera+lens. Perhaps I can give you more pointers if you specify which lens or lenses you wish to use.

If your mount is a fork then you do need a sturdy ballhead, but most folk do this all wrong and end up with major headaches with balancing. So, is it a GEM or a fork? Which lenses?