Your art will continue to grow as long as you want it to and as long as you pursue your talents...I know this may sound a bit harsh but it is now the time to start building your skills and taking your art to the next level. It is perfectly okay to do sketches on anything at hand, I know I have hundreds of scraps of paper with my stuff on it, cardboard box's, napkins, you name it I drew on it. It was when I started to take my art serious that I began to realize the potential of what may be possible. Also, I still sketch on any scrap of paper when I cannot get my hands on something more suitable because of an idea I have and I want to get it out on paper so I do not loose my train of thought. I only say this because you have great talent and ideas that need to be presented in such a manner that will be presentable and more complete. Have you ever used traditional quills and ink? If not I believe you would find them very interesting and will give you great flexibility in your work...regardless of what you end up doing, just keep creating!
side note; maybe think about a hardbound sketch book that you can keep with you and start filling that up, your work is worth it!