I recently came across of the ruby-2.0.0-p0 installation. After the successfully installation of the rvm i type the following command at the bash.
rvm instal
Open Up the Terminal and then Go to Edit > Profile Preferences and then go to the Tab "Title and Command" and Check "Run Command as Login Shell".
Boot Up a Bash and Now you can install Gems directly from the terminal without the use of sudo and the error "RVM is not a function, selecting rubies with 'rvm use ...' will not work." will be eliminated.
Cheers.