TBH I am a weird mix. I back up the things I really really care about, then delete a ton of other things to conserve as much storage as possible. I regularly go through emails and delete anything that isn't a newsletter I want to read or that I might need in the future, and move the ones I keep to different folders. I regularly check to makd sure photos on my device are only the ones I truely need/like. I go through the documents I download, and start deleting useless trash and then highly organizing the stuff I keep in folders. So I have like 58 GB of just Ebooks and audiobooks (The ebooks and audiobooks are mostly Project Gutenberg and Librivox ones, but I do buy a few modern Audibook CDs every so often and put them on there, and Google Play Books makes it easy to buy and download no DRM free ebooks) and then like 10 GB of music from CDs, digital marketplaces like Amazon Music, and Bandcamp, etc. But then I also don't really have many pictures or videos on my phone at all. I just hate the idea of buying things or spending money on them, and not owning them for real.