Hair Help Needed

Hi,

Im 21 year old male I have medium length brown wavy hair the top comes down to about my bottom of my eyes. I have been growing it out because I`ve always wanted that long hair look but I dont want to grow it to pony tail length. But the longer my hair gets the wavier and thinner it becomes. I would defiantly appreciate any advice that i get to what i can do with my hair to get that straight and more fuller look.