Number one, DON'T take herbs until after you hit 20. Otherwise, it will mess with your hormones, can cause terrible side effects, and can actually stunt your boob growth.
Massage, massage, massage! You're so young, so if you start massaging early, you'll greatly increase your chances of growing big, natural breasts! Massage will increase circulation in your breasts, and will get the hormones your body is naturally producing to flow to them! I just wish I had started massaging so young!
I'm not sure when puberty hit me. It was all over the place for me. :/ I started growing small mounds in like 5th grade (small as in maybe AA, but still more than some of my flat-chested classmates). Then I think in 6th or 7th grade I was a full 34A. And then I grew into a full 34B around 9th grade. Sometimes my breasts would even swell into a full 34C! But then my hormones went haywire around 10th grade, and I went down to a small 34B (didn't fully fit it anymore) and had all kinds of awful hormonal side effects. They put me on birth control because my estrogen was so low, I was getting period cramps so bad I would pass out from the pain. But my levels were so low at that point, even adding birth control didn't grow my boobies any.

I think the problems stemmed from my lack of eating (both from anorexia and the fact that my family couldn't always afford food). The best thing you can do for your growing breasts is to eat healthy! And try getting all your vitamins and minerals in to keep you on the right track. If you don't normally eat breakfast, try adding Ensure of Breakfast Essentials to get extra vitamins and protein in. Those things are essential to growing bodies.
Good luck, and massage away! Give it a few years to see what happens, then try listening to hypnotherapy for breast growth if you think you're not hitting your growth spurt as hard as you should be. You're still young, so don't rush anything, but do whatever you feel is necessary to help your body along the way!