Most any multi vitamin will help with over all health but you should avoid bandwagons and trends as far as using mass doses of suppliments that are intended for other purposes; you could have major health problems (or skin eruptions) for the sake of attempting to find a magic growth pill when they don't exist.
You need to concentrate on eating well, drinking lot's of water, and good hair handling habits.
Black hair is dry by naure, so you need to counteract this. Moisturize, avoid too much direct heat, if you use chemical processes then assess if there is any damage from that and find other alternatives (if you chemically relax, look for other ways to straighten the hair; if you dye-like I do- find the kindest way possible for your hair, etc..), your hair may not respond to certain additives or ingredients in certain shampoos or conditioners or styling products- even if it's formulated for "dry" or "black" hair.
You have to play around until you find one that your hair says "ahhhh, that quenched my thirst!".
Your hair is already growing, what you need is retention. Chances are, you are losing hair as fast as you are growing it and not seeing any progress but you can fix it, but you can't fix it by trying to bypass the work that it will take; even if you find a pill that will make it grow, it won't matter if it breaks of or sheds too much, right?
Manipulate your hair as little as possible and don't drown it with products. Don't use tight ponytail holder or metal barretts or barrettes with metal clasps- this will foil your efforts in retention because this are known hair snappers!
You'll be surprised by how much your hair will respond with a little tlc!