Do you think it's bad if I drive my car and not refill the gas tank?
Yes it is, why wouldn't you fill up the gas tank in your own car.
Gas costs too much, I'm going to try to get someone else to pay for it.
You are responsible for filling and paying for the gas you've used in your own car. The car won't run without gas and unless you've driven someone around and they plan to pay you for the gas you used, I don't see how you'll get someone to pay for the gas.
If no one else will pay, I've heard that the car will run even when it's on the empty line. It will be fine.
Trying to operate your car when it's on empty could damage the engine. It would be much cheaper for you to pay for the gas then repair a damaged car. Try to borrow money from a friend if you don't have any right now.