LowLifeFPV

I think i want to start a 500 size or bigger build. I have had a blade 180cfx for years with a few hundred flights and a blade CPX nano with a handful of flights. I've been flying quads, fixed wing, fpv, and everything else from micro to giant scale for about 9 years. Want to dive in on my first big heli build. Just got my hands on a few brand new 6s 6000 mah pulse batteries as part of a payment for help with another build.. I also have an excess of 4s 2600mah,, 4s 1300mah, and 3s 2200 mah batteries. Don't want to dive into nitro again. Using gas for big stuff and electric for everything in between. What should I build? I don't even know whats a good source to start looking at. Help me get started please.