I know that when using gem install, the gem will be stored under /home/username/.rvm/gems/, under which gemset the gem was installed.
But if I use Bundl
Note that gems are also installed into the bundle folder within your "Gem Path" (see: bundle env). This happens, for example, with gems installed from git:
gem 'my-gem', git: "https://github.com/x/y.git"
I assume this is so that custom installations don't conflict with installations from a gem server.