* This has only been tested with ubuntu 12.04 – you also already need gcc and ruby of some sort installed
These instructions allow you to run your own version of ruby and rubygems from your home folder

Download and install rvm
Set a couple of environment variables

bash -s stable < <(curl -s https://raw.github.com/wayneeseguin/rvm/master/binscripts/rvm-installer) 

echo '[[ -s "$HOME/.rvm/scripts/rvm" ]] && source "$HOME/.rvm/scripts/rvm"' >> ~/.bash_profile 
echo 'PATH=$PATH:$HOME/.rvm/usr/bin # Add RVM to PATH for scripting' >> ~/.bash_profile
. ~/.bash_profile

Install Ruby 1.9.3

rvm install 1.9.3
rvm use 1.9.3 --default

Install some gnu tools you need to install gems

wget ftp://ftp.gnu.org/gnu/m4/m4-1.4.16.tar.gz 
tar xzvf m4-1.4.16.tar.gz && cd m4-1.4.16/
./configure --prefix=$HOME/.rvm/usr
make && make install

wget ftp://ftp.gnu.org/gnu/gperf/gperf-3.0.4.tar.gz
tar xzvf gperf-3.0.4.tar.gz
cd gperf-3.0.4/
./configure --prefix=$HOME/.rvm/usr
make && make install

wget ftp://invisible-island.net/byacc/byacc.tar.gz
tar xzvf byacc.tar.gz
cd byacc-20121003/
./configure --prefix=$HOME/.rvm/usr
make && make install

wget ftp://ftp.gnu.org/gnu/termcap/termcap-1.3.1.tar.gz
tar xzvf termcap-1.3.1.tar.gz
cd termcap-1.3.1/
./configure --prefix=$HOME/.rvm/usr
make && make install

wget ftp://ftp.gnu.org/gnu/ncurses/ncurses-5.9.tar.gz
tar xzvf ncurses-5.9.tar.gz
cd ncurses-5.9/
./configure --prefix=$HOME/.rvm/usr CFLAGS=-fPIC
make && make install

wget ftp://ftp.gnu.org/gnu/texinfo/texinfo-4.13a.tar.gz
tar xzvf texinfo-4.13a.tar.gz
cd texinfo-4.13/
./configure --prefix=$HOME/.rvm/usr LDFLAGS=-L$HOME/.rvm/usr/lib CPPFLAGS=-I$HOME/.rvm/usr/include/ncurses
make && make install

Install some more tools you need to install gems
This time just use the ones that rvm has packaged
# ORDER MATTERS !!!

for i in curl zlib readline openssl iconv pkgconfig autoconf libxml2 libxslt libyaml ; do rvm pkg install $i --verify-downloads 1 --with-opt-dir=$HOME/.rvm/usr ; done

Reinstall ruby 1.9.3 with the new path of your tools compiled in

rvm reinstall 1.9.3 --with-opt-dir=$HOME/.rvm/usr

Install the ‘fog’ gem

gem install fog

Your home folder will now be 1.4GB large but you’ll have a self contained ruby and rubygems installation with the fog library available