I had a similar problem working over a metered cellular data connection recently. One thing that helped a lot was the uBlock Origin extension for Chrome & Firef

I had a similar problem working over a metered cellular data connection recently. One thing that helped a lot was the uBlock Origin extension for Chrome & Firefox, which has a feature that prevents automatically loading media elements over a certain size (say, 50kb). If you want to load a large image or video you can click to load it or turn the feature off on a per-site basis. Can use it in Firefox on an Android phone, too, since it has extensions.