we do not need to use sudo to install gems, as everything is kept in ~/.rvm
It's not that you don't need to, it's that you shouldn't. Using sudo to install gems will do so outside of your rvm gemset, and so the gems you install this way will not be available to your app using the gemset.
It's not that you don't need to, it's that you shouldn't. Using sudo to install gems will do so outside of your rvm gemset, and so the gems you install this way will not be available to your app using the gemset.