Normally you don't really want to install stuff from source unless you have to because Ubuntu provides you with software updates so that you don't have to go out and update everything yourself, but unfortunately since they aren't as timely as we would like with this particular software it's alright to make an exception - especially since it has an update feature built-in.
So to install Rubygems from source, you can use this at the terminal (make sure to check and see if the version has changed, since I won't be able to constantly update this post):
wget http://production.cf.rubygems.org/rubygems/rubygems-1.3.7.tgz tar -zxvf rubygems-1.3.7.tgz cd rubygems-1.3.7 sudo ruby setup.rbYou should be able to just follow the instructions that it prints out and it will do what it needs to do. Then when you want to update the actual rubygems software:
sudo gem update --systemSimple! This way you don't need to depend on the Ubuntu package maintainers to update the software for you, and you can use all of the latest-and-greatest gems that come out each day.