One of the reasons this becomes difficult, particularly when responding on a board like this, is that things change quickly. You are talking about multiple operating systems, multiple versions of ruby, multiple versions of rails, multiple tools for managing them. I still see questions on Rails 2 and, quite frankly, that was so long ago I don't remember. On top of that, you will be faced with choices such as rbenv vs. RVM, ERB templates vs. HAML, etc. and everyone has their arguments as to which is better.
My advice to someone starting out is not to use the standard rails docs. The edge guides are very well written but, to me, they are more of a reference. I would start with a good tutorial. Be default, the tutorial will make these choices for you, but will give you detailed instructions on installing and using them. For example,
www.railstutorial.org is one that is commonly recommended (and I recommend it as well). That particular tutorial uses RVM, ERB, and Rspec. Once you have a basic understanding, you can then explore the other options and determine which are best for you.