I'm not sure exactly what your intended use is - filming yourself, others, above or below water but here are a few things I use. The clamp can be handy along a stream or in the woods but for a boat, a permanent mount may be better. For underwater stuff, I use a RAM adaptor with an Ettore painters pole. If you want to get fancy photos, try an over/under dome attachment. I have the Telesin model but it looks like there is some competition out there and I assume there is one for the newer GoPros.
RAM Pole Adaptor
Telesin Dome Port (Hero5)
An extra battery and the double charger is handy. A chest strap or sportsman's mount may also be good depending on your needs.
Have fun with the new toy!
Jon