I'm thinking of possibly leaving my ex with not much in the apartment
Are you getting rid of everything?
Yes, I'm giving them some of my old clothes also
Ending a relationship is hard so it is understandable wanting to get leave and get rid of everything that reminds you of it. It can help you move on.
I'll be fine with just one backpack and leave my job.
Just don't leave anything that you may need or miss. Getting started in a new life outside of a long term relationship is hard and expensive. Take your time to think through what you will need and make healthy choices for yourself.