Genesis consists of a framework and there are also a set of child themes on offer. You can buy the child themes individually, or as a pack containing all of them. Admittedly you could start with just the framework, but that’s probably making a lot of unnecessary work for yourself.
But what if the child themes are not really what you’re looking for?
Well now, to get you started, StudioPress have started releasing free child themes that are somewhat more basic, but still a good place to start if you intend to customise the theme yourself.
Just visit the StudioPress website, click on “Resources” and download them!
Of course, if you don’t yet own the Genesis framework then you will need to purchase that first.