I installed ruby via rbenv

Use rbenv https://github.com/sstephenson/rbenv

$ git clone git://github.com/sstephenson/rbenv.git .rbenv
Add ~/.rbenv/bin to your $PATH for access to the rbenv command-line utility
$ echo 'export PATH="$HOME/.rbenv/bin:$PATH"' >> ~/.bash_profile
Add rbenv init to your shell to enable shims and autocompletion
$ echo 'eval "$(rbenv init -)"' >> ~/.bash_profile
$ wget  http://ftp.ruby-lang.org/pub/ruby/1.9/ruby-1.9.2-p320.tar.gz
$ tar xvfz ruby-1.9.2-p320.tar.gz
$ cd  ruby-1.9.2-p320/
$ ./configure --prefix=$HOME/.rbenv/versions/1.9.2-p320
$ make
$ make  install

Restart your shell so the path changes take effect
$ source ~/.bash_profile

Set your default Ruby to be version 1.9.2
$ rbenv global 1.9.2-p320

After installing gems (gem install or bundle install) run rbenv rehash to add new shims
$ rbenv rehash
$ gem  update  --system
$ gem  install  bundler
$ gem  install  rake
$ rbenv  rehash