I installed RVM using the single instruction mentioned at the RVM website (using git).
Then I installed Ruby version 1.9.2 and 1.8.7 using:
rvm insta
I had similar problem (using Ubuntu 13.10) to solve it
$ source .rvm/scripts/rvm
and for long term
$ echo "source ~/.rvm/scripts/rvm" >> ~/.bashrc
$ ruby -v
The program 'ruby' can be found in the following packages:
* ruby1.8
* ruby1.9.1
Try: sudo apt-get install
$ source .rvm/scripts/rvm
$ ruby -v
ruby 2.1.0p0 (2013-12-25 revision 44422) [x86_64-linux]