I am attempting to use
sudo apt-get install ruby-full
$ bundle install
$ bundle exec rake
$ sudo apt-get install bundler
$ gem install bundler
$ sudo gem install bundler
$ sudo bundle install
Don't run Bundler as root. Bundler can ask for sudo if it is needed, and installing your bundle as root will break this application for all non-root users on this machine.
I've been working with Ruby only a few weeks now. I'll say, I know where you are. I am not about to help much but will say, to your last question in the comments, that my understanding is that the two commands are different.
My understanding of a short answer.. One can have diff versions of Ruby they need to work with (legacy projects, etc) and not every version of Ruby can run every version of a given gem. For this reason, one can use rbenv or rvm to help manage the art of setting up a project with a particular version of ruby and then installing the needed gems.
I've been working with rvm on my mac and rbenv in linux and find them both similar enough for the simple stuff I've been doing. Installing rbenv on linux proved slightly easier. Once set up properly, sudo is no longer needed to install gems - which is preferred. I would recommend trying one of these and installing per their website instructions. Things should go smoother once set up.