I used this guide: http://pragmaticstudio.com/blog/2010/9/23/install-rails-ruby... when getting started, which was pretty painless.

There's also a GUI for RVM called Jewelry Box which makes handling gem sets and ruby versions easy: http://unfiniti.com/software/mac/jewelrybox

I think the money would be better spent on creating a comprehensive beginners guide since the 4th edition of Agile Web Development with Rails is lacking.