How do i grow my hair without spending tons of money?

Alright! being 15 and in high school I'm definitely that girl thats wants to be in style! i am mixed with black so my hair is very curly and kinda thick. i do straighten my hair a lot which i realized is damaging pretty badly! i cut my hair not to long ago "thinking" i would grow to love it! and getting rid of all the dead ends. instead i wanna cry because it refuses to grow! i do tend to dye my hair more then i should cause i'm the kind of girl that gets tired of things quit easily and i need change. so far i've heard some pretty interesting tips on how to help it grow, but I'm only 15, i don't have a job, and my mom isn't going to go buy me all the vitamins or oils i need to help it grow! is there anyway i can help my hair grow in a healthy un-expensive way? i miss my long beautiful hair and unfortunately its not going to magically grow back like i hoped! WHAT DO I DO???