Hello,

As to make Firefox faster and save some data, I recommend downloading the add-on Ghostery from Mozilla add-ons. This can make FF faster by:

   blocking advertisements
   blocking analytics (track you and use up data) 

blocking beacons (useless for browsing, just for tracking)

Ghostery can dramatically increase browsing speed!

Also, try some of these things (particularly #8 to compress data) http://www.techradar.com/us/news/software/applications/8-hacks-to-make-firefox-ridiculously-fast-468317

Also, refer to this thread to prevent the loading of images on a page... https://support.mozilla.org/en-US/questions/961547

Firefox does not implement this feature because it requires all your browsing to go through Mozilla controlled servers.

Google and Opera do this by sending all the requests you make to visit websites to servers they control. This server proxies the request to the site you actually wanted to visit. When the site you wanted to visit responds with the content the Google or Opera server compresses the images and strips out other things that are not needed.