Preparation was for a month, a couple of hours every day, almost consistently. I've been using Linux for several years, and wrote the LPIC-1 cert a couple of months ago, so I had all the fundamentals down already.
My primary resource was the RHCSA course here on LA. I went through every single video, quiz, exercise and live lab, doing some multiple times till I had it down. I also studied the official exam objectives on redhat site to make sure there were no holes in the course (which there aren't). Finally, I used an assortment of web pages that I found from googling around to get further insight on some topics, most notably certdepot.net. That site is an absolute gem for Red Hat certs with several quiz and practice tests you can try out.
My lab setup was basically my laptop with the "no-cost" Developer version of RHEL installed on it and several VMs on that with virt-manager.