Hi and welcome.
The best starting point is submitting a one minute test and the team there will guide you on getting your setup right.
http://wiki.librivox.org/index.php/1-Minute_Test There is no need for an expensive mic... a decent USB mic can be bought for about $20 on Amazon. Of course, you can pay a lot more for a better one, but best to see if you enjoy recording before forking out
When you start, it is best to read a chapter or two of established projects, but once you are familiar with the site and the process, you can branch out to any Public Domain text that interests you.
Lynne