We recommend Ruby 2.0.0 for use with Rails. We stopped supporting Ruby 1.8.x after Rails 3.2. Ruby 1.9.2+ will be supported until Rails 5.
We recommend managing your Ruby installation through rbenv. It's an easy way to run multiple versions for different applications and update when a new release is made.
With Ruby installed, you can install all of Rails and its dependencies through RubyGems on the command line:
gem install rails
New versions of Rails can be installed the same way.
Make your application
Create your application skeleton and start the server:
rails new path/to/your/new/application
You're running Ruby on Rails! Follow the instructions on http://localhost:3000.