I've been setting up multiple Ubuntu machines from past 1 year and so writing down the steps that I have compiled after hours of frustration and research.

DISCLAIMER : There are steps like these on many blogs but they did not work for me (hence this list). The steps mentioned below may also not work for you.

1. gpg --keyserver hkp://keys.gnupg.net --recv-keys 409B6B1796C275462A1703113804BB82D39DC0E3
2. \curl -sSL https://get.rvm.io | bash -s
3. logout and login again (close the terminal and open it again)
4. type this on the terminal window : source ~/.rvm/scripts/rvm
5. Check if RVM was installed properly, type : rvm | head -n 1 (output should be “=rvm”)
6. rvm install 2.2
7. rvm use 2.2
8. sudo apt-get install nodejs
9. sudo apt-get install git
10. sudo apt-get install libmysqlclient-dev
11. sudo apt-get install libgmp-dev
12. gem install mysql2
13. gem install bundler

After this point, you should set up your directories with your code in the server. Once you do that then do these steps

1. bundle install (do it in all the code directories)
2. sudo apt-get install apache2
3. sudo apt-get install libcurl4-openssl-dev
4. sudo apt-get install apache2-threaded-dev
5. gem install passenger (first try without sudo, if it  fails then prepend “sudo” and run the command again)
6. passenger-install-apache2-module (if you used sudo in the above step, use sudo here, else don’t)

Now sit back and relax or grab a cup of coffee. Passenger will take around 10-15 mins (depending on your internet connection speed) to finish.

Once its done, it will print a configuration on the screen. Copy that and do the below step

1. cd /etc/apache2
2. sudo nano apache2.conf
3. go the bottom of the conf file and paste the lines you copied
4. Now do this : cd /etc/apache2/sites-available
5. sudo nano 000-default.conf
6. add the below lines at the end

  
    <VirtualHost *:80>
      # Change these 3 lines to suit your project
      RailsEnv development
      ServerName dev.blah.com
      DocumentRoot /your/website/path/public # Note the 'public' directory
    </VirtualHost>
  

Hope this helps!