How can i make my nails grow longer?

-My nails get really pretty when they get longer but they tend to break easily how can i make them grow longer? i usually like to do my nails my self usually dark colors. I bought this polish that says growths spurt its supposed to make them longer, healthier, and stronger but what else can i do to make them grow faster i have till august 22 because thats when i start school. Oh and im 15 and broke so i cant really buy anythingIf you bite them, put acetone (nail polish remover) on them so when you stick them in your mouth it tastes really bad! Try not to wear nail polish ALOT. Just put on a nail hardening clear coat to keep them strong. i take a multivitamin that will help with keeping my nails stronger. I also heard just putting ground up garlic and olive oil on the nail bed helps too. You can also make them look a bit longer by pushing back and remove the cuticles. Also file them once a week so they dont grow a little uneven (:
idk what product you use but i use Nutra Nail Mineral Nail Care Power growth. it works amazing. they should be longer in like 4 days of using this and a lotttt stronger. trust me! i love this stuff. its not expensive either. i think i bought mine in target. good luck!!
I have heard that eating Gellatin (Jell-O) makes fingernails stronger.
Don't wear nail polish often and trim them every now and then.