What percent of money should I be saving?

I just turned sixteen and I’ll be getting a job soon. I got about three hundred dollars for my birthday also and I want to start setting some money aside. I already have a checking and savings account (I already have a car so I don’t have to save for one). So what percent of my overall income should I be saving? What are some saving tips? What percent of my income should be disposable?
Well, no bills really. Just filling my gas tank (11 miles to the gallon) and tithing in church.