How Can a 13 Year Old Try NOT to Spend Any Money?

I am 13 years old, with a $5 weekly allowance. Well, it used to be $10, but since I got a phone, it lowered. I want to save up for something I want to but, like an iPod, or a drawing tablet, but so far, i only have 10-15 bucks! I spend my money on the little food mart after school, or at a little art supplies shop. I let my mom borrow money because she really needs it. How can I make myself not spend any money? Any advice or tricks wll help me alot! Thank you!