Hair extensions for thick hair that are not very expensive?

My hair is really thick and sorta straightish wavy, and to me it seems like its always been the same length for ages, my dream is to have pretty long hair like...down to my elbows, or something like that. So i saw that for now i should use hair extensions. I was looking for some that are good quality but not expensive, like not over a hundred. Does anyone know where i can get these online?
Thanks!
ps: if their slightly over 100$ its ok...