I recently bought a good SD card designed for smartphones where everything except apps and cache can now sits (pictures, files, etc.) And I gained almost 3gb in my internal memory.
The SD card is formatted as extra storage and I can even run apps with it (accidentally got Pokemon Go reinstalled on a “temporary card” I tested, and it ran unexpectedly well for a snail slow card) and now I even watch entire videos on my phone, like several gb of movies.
I’d recommend that you get a SD card designed for smartphones (there should be a A1 on the card) for Christmas or incoming sales if you have nothing in mind. You will absolutely love it!
Make sure to check the compatibility and speed of your device, if you can add a SD card as active storage, and keep in mind that your SD card used in such a manner will become part of your device and you won’t be able to use it in another device even to transfer files…
I think I covered everything… Now questions will have to wait till tomorrow Night!