Keep it simple. Seriously, do not over-experiment, it causes setbacks and I know that personally. Stick to what works and your hair will thank you for it. It's great to try new things but I would say be cautious and don't do too much at once.
Take vitamins, eat healthy food, exercise, drink lots of water, and get enough sleep. Water gives your hair moisture and your body repairs and grows while you sleep; exercise helps will blood circulation; taking vitamins and eating healthy food will help nourish your body from the inside out. Green smoothies are a good way to get lots of nutrients and all you need supplement-wise is a multivitamin, 5000 mcg biotin, and fish oil. If you want to add some extras, MSM, silica, and collagen protein are great – talk to your doctor first before starting a new vitamin routine, btw. It's okay to cheat and eat fast food 1x-2x/week if you really like your treats but the majority of the week, you should be giving your body healthy food because it really shows in your new growth in terms of strength, shine, luster, etc.
PATIENCE. Your hair is not going to grow overnight and all what I wrote in the previous paragraph is going to take at least 3 months before you'll see some sort of result. Waiting sucks but it's necessary.
TL;DR - If you keep it simple, have patience, drink water, eat healthy food, take vitamins, and sleep your hair will grow with ease. Exercise is the icing on the cake but plenty of people don't exercise and have long hair. Good luck.