The intent is that:
- master is stable and has been tested with at least one project
- develop is expected to be stable, but needs some testing
- feature branches might be completely broken
So small incremental improvements should be done on the develop branch and then tested against at least one project before being merged into master.
If you're doing something bigger, then please make a new branch. Once it is working, merge the develop branch into your feature branch, check everything still works, and then merge your branch into develop. Alternatively you could make a fork and merge back in via a pull request, so it is easier to do a good code review of your changes.