Jim's LG phone is constantly being filled up. Leo says that's because it's an 8GB phone and the OS itself takes up over half of it. That's why they can give these phones away for free. Nobody really should sell an 8GB phone.
Jim can clear out temp files and get rid of unused apps, then save all of his photos and videos to Google Photos. He can do the same thing for music with Google Play. Ultimately, Jim just needs a phone with a larger storage capacity.
One thought is to add an SD card to the phone, if it supports it, and he can then install apps onto that as well as data. If his phone doesn't have that, he's kind of stuck.