How do I get rid of my acne??!!?

I'm 13 and I have really bad acne. I've had acne since I was 11 and I didn't really care to much about it until now. I had dry skin and then I used a mostuizer, which worked, but then about 3 weeks later, I got oily skin. I've stopped using that stuff, but with my oily skin, I've been getting more pimples! They're everywhere on my face. I haven't tried using any products because they're so expensive and I wasn't sure if they'd work…. Please help.