I hope I'm not stepping out of my lane on this one, so I apologize if I do.
You're 15 my man. I believe Cback is the one who mentions this all the time on here so I will take a page from his book. You're 15. Your main focus should be school, sports, hanging out with friends, and trying to get laid. I would advise (based on personal experience) sitting back and taking in the site. Don't post. Just read. Even if the thread doesn't interest you personally, you will learn something new. See how the professionals on this site address issues and each other and be a sponge. It will save you a lot of time, grief, and save you from being called out from a stupid post. I don't think there's a person on here with an Aspiring SOF under their name who hasn't seen the wrath of mods/admins due to a stupid post. ;)
That said, it's awesome you're 15 and have those goals. But you're 4 years away from being eligible to join. Go live it up. I don't know a single person who wishes they didn't do more fun/stupid shit while in high school.