iTunes taking up 33GB space, without any media

The graph you are referring to uses the Spotlight index to calculate storage and the index is easily damaged. Right now it is telling me that iTunes is 7.4GB but a quick check shows that my iTunes folder contains 14GB of music I own, 7GB of movies, and 3GB of music I've downloaded from my Apple Music subscription. How this becomes 7.4GB is a mystery 🙃 unless you take the bug/damage into consideration.

For the purposes of knowing how much drive space I have left, I select my hard drive icon and use Command I. If I want a rough estimate of how much music I'm holding, I find the music folder and use Command I. (get Info). If I want something more fine grained than this, I use DaisyDisk a shareware disk management program.

When it comes to deleting files to free up space, for the most part, what is taking up space is irrelevant. Deleting applications usually doesn’t help - except for fancy games. Apps don’t take up that much space. Documents don’t either. If you need free space head right to your videos and music.

That said, when I purchased my first MBA in 2011 I was moving from. 750GB drive to a 256GB drive. I combed that computer like crazy, and discovered that my Library folder was full of stuff going all the way back to MacOS 10.2. It can be dangerous to delete files from your library unless you know exactly what you are doing. In my case I found tons of support files for programs I stopped using years before. But again, the typical user should look to media files to free up space.