#Rails Basics Quick Start
$ rails new 'your app name' --skip-active-record
alternatively -OT can be substituted for --skip-active record.
The O is the skip active record equivalent, and that T, yep it skips testing.
The gemfile loads all of the gem configurations and dependencies you will need for your application. This is a top-level file within your app, called, you guessed it, gemfile.
Insert this line : gem 'mongoid', github : 'mongoid/mongoid' you have to run bundle in your terminal to execute gem installs.