Well, I was about your age when I began learning cake decorating. Just focus on one technique at a time. You have an advantage I did not in that there are some amazing tutorials online including a lot of Youtube videos with amazing instruction. I would recommend that you look at websites of people who produce amazing work and then research and find out if they have produced instructional videos. Edna De La Cruz is one of my favorites.
I started driving my mother crazy in the kitchen by the time I was tall enough to see over the counter! By age 7, I was cooking and baking and by 13 had mastered breads, pies, and cakes and then went on to master cooking. In my 20's I began to learn cake decorating and have self taught myself pretty much everything by trial and error. I made celebration cakes for family and friends for over 20 years while working a career. A few years back I was able to quit my job and focus more time on my children and my own interests. I had more time so I began learning even more about caking and people began to beg to hire me. Thus, three months ago I opened my home based bakery. I have a website if you would like to peruse some of my work. It is: www.letmecallyousweetart.com