How should I budget my money?

I am paying my parent back for buying my car. I owe them $865. I have a job and make about $440 per month. I also mow 2 yards and do chores. So I make about $550 per month. How much should I put towards my car in case it breaks down or needs parts? And how much should be be outing towards my debt? Anything else I need to be budgeting on to help me or my future?