Well, first you have to decide what kind of website you want to make. Is it a news site, where you post articles and invite others to do the same? An arcade site? A forum site? Or something else?
What you may want to do, and which I suggest all writers do, is to create a website about yourself where you post your literary works. A good example of this is one Snoink made: http://snoink.net/
Another possibility is to create a site where you just upload stuff about yourself. I used to do this with my personal site: http://www.nathancaldwell.com
If you decide to instead go the forum route, you have to decide what your forum is going to be about. If you do this, it should be a very narrow interest (you can broaden it out later). For example, instead of making a forum devoted to video games, make one devoted solely to your favorite video game (ex. Super Mario Galaxy 2). As time goes on, you could slowly broaden it out to games in the same series (all Mario games), and then slowly to all video games (in this case, first Nintendo then to Sony & Microsoft).
Or if an arcade site, decide if you want to include any type of game, one type of game, or just one game. One great free tool for doing this is phpbb arcade. If you decide to go the one game route, then an RPG like Legend of the Green Dragon / Dragon Prime is your best bet.
Overall, I suggest the personal website route as it'll prove beneficial in the long-run. First, creating a site where you talk about your novel progress and post your literary works will help you grow as a writer. But secondly, creating a site about yourself will bump that site to the top of the Google search results when people google your name. That's not a big deal at your age, but once you start applying for university or start looking for a part-time job, it'll help. Admissions officers and employers almost always use Google these days to check out prospective students/employees. If your own site is at the top of the search results when they do this, then you'll have control over what they see.
A good place to find Domain names for fairly low prices is www.1and1.com or www.1and1.co.uk - it's where I got mine from. They have a reliable website constructing service, an optional forum and some great set-up CMS softwares, but it isn't free unforunately.
