This is mostly personal and what works for you, but you probably do not need more than 24 inch size bag. But there are people that put a lot in their bag and you might need something larger. But 36 inch bag is probably a little much for basketball as you do not have to put an actual basketball in the bag.
Most of all this is what you are comfortable with. Do you want rollers or spinners on the bottom of the bag. It is mostly about what you are comfortable with and how you want to look.
Peace