One good thing in recent Ruby on Rails are Gem Dependencies! However.. they are very frustrating when you need gems in your plugins. This gives you a Catch 22..
The rake task to install gems:

1
sudo rake gems:install # Use sudo! See notes below

gives you an error like:

1
2
3
4
5
6
sudo rake gems:install
(in /your/rails/dir)
rake aborted!
no such file to load — […]