How to control, monitor and limit bandwidth usage?
There are several things you can do:


Restrict background data. You'll find this option in the Data Usage section of Settings.


Use an ad-blocker like AdGuard or Adblock to avoid wasting bandwidth on ads.
Navigate to the Settings page of your data-guzzlers and make sure they only do their data buffets over Wi-Fi.
Also do remember to check your Data Usage page regularly to stop any greedy apps you've forgotten about from chomping down all your data.