Agree with the above posters. Don't be put off by anyone claiming that it's only for geniuses. They're full of crap.
I'm close to releasing my first game, after c. 1 year of dev during which time I taught myself C# to develop the game via unity. If I can do it, I'm sure you can. (when I started I was just familiar with computers, having played a lot of computer games during my life ). Btw, I'm 30, so you've got 12 years on me as well
My tips, based on the last year:
1. Pick sensible starting projects - if you're new, I'd say start with a 2D game. You can worry about the z-axis later. It's perfectly possible to make a 2D game that everyone loves, and it's much easier than making a full 3D world.
2. Break larger problems down into smaller ones - a video game is a huge collection of things, like art, audio, game design, and programming. And each of these is another collection of smaller areas. Tackle individual areas individually. Make lists, they help. It's easy to get overwhelmed by the size of the whole project, so don't worry about things until you have to. Not got an idea for a game yet? Then you probably don't need to worry about all those complicated programming language tactics. etc.
3. The easiest way (I found) to learn programming is to do it on a project you love - don't try and learn a whole language abstractly. Learn what you need to know in order to build the game. It's more fun that way (you get to see a result of your effort). It's like learning a foreign language. You can study books all you want, but it's putting it into practice that really cements it in your brain.
4. Read stuff - There's plenty of info online and in books about various topics. One of the best bits about game design (for me) is the wide array of stuff you get to read about. I've read about audio design, coding, AI and tons of other stuff. Especially when you're just starting out, find some good sites and read them, they'll help a lot. ALSO - there are some good online resources for learning the basics of coding, and you can do some free lessons online. They were really helpful for me.
Other than that, I'd say just dive in. Think about a game you want to make (that isn't too complicated - see point 1), and start to crack on with it. It's tough, but if you persevere, it can be very rewarding.
I would also recommend using a game development engine (I use Unity, it's great). They're really useful, and you can get started straight away. They also take care of lots of basic things for you (like physics) and provide you with a whole array of in-built programming tools and methods that make starting out much easier.
Trust me, the only barrier to success is yourself, and your discipline. You're 18, you've got all the time in the world!
Best of luck!
PS: if you want to check out my game that I've almost finished, the website is here. It's a doctor simulation game inspired by Papers, Please.
PPS: Forgive the shameless PR, but as this good Gamasutra article says, you have to be tenacious with your game dev PR