The first thing I did when I was preparing for a certification exam was perform the Administration Course training available on the nutanix education portal, this course is recommend for certification.
I Looked to the community for support. There are lots of blog articles on specific exams, learning objectives, and lots of decent materials out there and now a number of books available.
With a bit of SSD storage, a bit of RAM and VMware Workstation you can build some pretty kick-ass lab environments.
You can always Test Drive CE for absolutely free here.
Good luck and put in your study time