I think you should start would just taking a regular multi-vitamin.
Actually there's so many supplements out there. GNC Ultra-nourishment, Nature's Plus Ultra Hair Plus, ETC.
The main ingredients that mostly everyone use is Biotin and MSM.
For some fast results... HF37 AND Viviscal are great. And what some people have done is instead of spending 89.00 on HF37.. they look at the ingredients from HF37 and buy the ingredients.
Also protein-filled shakes... whey powdered and soy protein are wonderful for the hair. And also just eating the right foods, drinking 8-12 glasses of water is a start. AND LETS NOT FORGET EXERCISING!!
The main thing is .. hate to say.... trial and error on the supplements. Most people swear on the biotin.. but its just you have to find what works best for you.
Hope this has been a help