I made a gem (Just on its own, not using bundler). I couldn’t get it to work at first. It was because I had named it with the .rb extension. Everything needs to be named the same though. It all has to match up. So I changed the name, dropping the .rb, uninstalled the gem, deleted the .gem files, built the gem again, installed the gem again. And it ran!!!! Super coolio.
For Greeter gem:
gem uninstall greeter
delete .gem files
gem build greeter.gemspec
gem install greeter