I'm not a professional composer, nor do I have a degree in music, or any musical "credentials" of any kind, but I think my answer might be useful nonetheless.
The extent of my musical experience is as a member of band/orchestra throughout middle school and high school, and about 3-4 years of piano lessons within that time frame. There was a point in time, when I was about your age, where I thought I wanted to be a musician. As I got older and into high school, and found out what a career in music realistically looked like, I realized it wasn't for me.
But I was still passionate about music, and I always took music along with me. I studied something completely unrelated in college and focused most of my energy on getting good grades and getting a good start on my career, but on the side I had an old version of Sibelius that I would tinker with from time to time. I never was able to complete anything substantial, but it was a good way to feed my creativity and keep my passion for music alive.
Fast forward a few years, I'm started in my career, I've got a lot more free time now that I'm not engulfed in my studies, and I've got some extra cash from my job. So I say to myself, "You know, now that I've got my job and cash flow figured out, why don't I take another stab at composing in my spare time?" So I went online and did some research, and before long I got my hands on a DAW and some decent samples and was making music again. This time however, with the tools I have available, I am much more satisfied with the music I am making, and I can make pretty convincing audio files with the quality of samples available today. It's not as good as a real orchestra, but it's pretty cool to have an audio file of something I wrote that I can listen to in my car as I drive around town.
The best part about this is I can write the exact kind of music that I want, whenever I want, without any restriction. If I were doing this professionally, I would have to write ALOT of music that I might not necessarily want to because the job requires it, I would have to make many artistic compromises with directors/producers/etc. that want a specific sound for their medium that I might not agree with, and I would have to meet strict deadlines, all of which would hinder my creativity.
In addition, with the technology that exists nowadays it is entirely possible to make very high quality representations of your music using just your computer. Just listen to some of the audio on this site as an example. Does it sound as good as a live orchestra? No, but you can still produce a decent quality audio file that is enjoyable to listen to.
I guess what I'm trying to say is it is very important to be fulfilled by the music you make. I can honestly say that even with the path I chose, I am still able to make music that fulfills my passion. Will my music ever be performed? Probably not. But I am incredibly satisfied with the music I am able to make with orchestral libraries I have available (and untrained listeners can't tell the difference from a live orchestra anyway lol). Had I chosen a career in music, I don't know that I would be making music that is as fulfilling as the music I make now. I have met a few professional composers that are burnt out and exhausted from writing music they are TOLD to write, instead of music they WANT to write. Putting a price tag on your passion changes everything, and I realized a long time ago that you should never sell something that you love.
At your age you should be doing exactly what you're doing. Compose because it's fun. Explore your passion for music. But I would also say to try other things you might be interested in as well. Take an art class. Take wood-shop. Join the debate team. Get out of your comfort zone and try new things. As you get older, these opportunities will go away, so take advantage while you can.
I'll touch on the career aspect below, but as far as skills go: curiosity. Always ask "why?" Why did this one composer structure this piece that way? That one part in this piece sounded cool, why is that, and how did he/she do that? Why did this instrument get the melody in this section? How did the composer achieve that really cool sound in this other part? etc.
Also: learn, learn, learn. Get your hands on books and study. Harmony, counterpoint, orchestration, etc. Find scores from your favorite composers and study them. Do what they do. You will sound like them at first, but as you experiment you will develop your own voice.
I would advise you to try to meet people that work as composers and ask them about their career. Ask them what their typical day is like. Ask them how they got there. Ask them what school they went to. Try to find out how much money you could expect to make. You need to be very aware of the lifestyle you can expect. This site is obviously a good source.
Lastly, (and this is important), if you decide to go into music, pick the right school for you. But don't base this just off of what people say about the school, try to find people who graduated from that school and ask them about their career opportunities. Ask them what it was like to study music there, and what kind of jobs they got when they graduated. Try to find people that just recently graduated, people that graduated 5 or so years ago, and people that graduated 10 or so years ago. If you really want to be a film or game composer, but you find out that most people that go to that school become band directors, or lesson teachers, or something unrelated to music entirely, then you shouldn't go there. There's nothing wrong with any of those jobs, but it doesn't make sense for you to go to school there if you don't want to do those things.
Sorry for the long-winded response, but I hope this helps at least a little. If you want any more advice, feel free to message me.