17 yo son has a job, which finances should he be responsible for?

So our 17yo old got a job a couple of months ago. He makes roughly 500 every 2 weeks. We want to teach him some financial responsibility for the future. We told him he should be putting at least 20 to 25 percent in savings. But what about expenses?

Would it be reasonable to ask him to pay 100 a month to cover part of his phone bill (120) and gas (no license and we drive him to and from every shift).

We agreed to still pay for everything when it comes to food, clothes, etc...unless he wants something super expensive.