Recently I realised I had +1GB of gems installed so I decided to uninstall all of them. I did this by deleting the gem folder content, but guess what?? Seems it's not the way to go, bundler says I have gems installed and running any gem command resulted on an error ofcourse because the files aren't there anymore.
First lets check the size of the gems folder with this command
du -h -d 0 `gem environment gemdir`
So, here is my tip for you! If you need/want to delete your gems use this command
gem list | cut -d" " -f1 | xargs gem uninstall -aIx
You now have a clean gems folder, more free space and probably a more responsive ruby system.
Thanks to http://geekystuff.net/2009/01/14/remove-all-ruby-gems/
Happy cleanup! :)