When I install gems on my server I do not get any of the documentation which is normally 3-5 times larger than the gem itself. Installing gems with out docs can be done via

$ gem install --no-ri --no-rdoc gem_name

Based this blog post I have created a ~/.gemrc so that it does the no docs automatically.

:update_sources: true
:bulk_threshold: 1000
:sources: 
- http://rubygems.org
- http://gems.github.com
gem: --no-ri --no-rdoc
:verbose: true
:benchmark: false
:backtrace: false