When I was 15 (1997) I was pretty decent in C/C++, Java, Pascal, and HTML/CSS. There weren't really webapps yet, or at least any way to deploy them, and not any way I knew of to work remotely or ask questions of other programmers like there is today -- so I didn't make much money at it and ended up working bagging groceries at my local supermarket instead. So definitely you have a huge heads up on my generation just by what you have. Simply asking this question (including the useful advice I'm sure other HN contributors will offer you) is a great step forward for you and a huge one for mankind.
I think the most important thing for you to do, however, is follow your passion. If you are passionate about math, complicated computer science questions, creating apps that make people happy, or something else. My pops strongly pushed me toward MIT but I ended going somewhere else and doing something other than engineering that I ended up finding a lot more passion for and that, even though I haven't (yet!) made a gazillion dollars in silicon valley, I've learned a few other human languages and enriched myself in a number of other ways.
So my advice more generally is don't be super narrow if you don't want to be. Get out there and experience the world and other things if you are excited about that. Don't worry about making a flashy web app, unless you have a vision that requires a flashy web app to be executed upon. There are a lot of people in this world doing a lot of different things.
Anyways, it may be true that your ideas suck. Ideas can be big (usually they also require large teams for implementation) or small (and potentially growing from an existing need you have yourself or an observed need of a community -- e.g. no apps for cats on iOS). If you need an idea, observe a community, know a market, ask people more specific questions, then execute.
Do you need to make money? If so, how much? That's a good question to ask yourself now since there is often a tradeoff between coding for cash and pursuing other interesting problems (things like Project Euler certainly don't hurt either way).
However, potentially the most useful piece of advice I have for you is go social. I didn't do that myself until later in my career, but I found it helps tremendously. Find a project that you are excited about and start contributing code (even if it is a very minor way). Your code will get better much faster if other people are reading it and esp. if other people who know what good code looks like critique it. In fact, probably the folks who contribute to such projects will be more valuable critics than profs at Stanford or wherever else you end up (not that it isn't a bad idea to get a good education, but remember that's not all there is to the world).
I think the most important thing for you to do, however, is follow your passion. If you are passionate about math, complicated computer science questions, creating apps that make people happy, or something else. My pops strongly pushed me toward MIT but I ended going somewhere else and doing something other than engineering that I ended up finding a lot more passion for and that, even though I haven't (yet!) made a gazillion dollars in silicon valley, I've learned a few other human languages and enriched myself in a number of other ways.
So my advice more generally is don't be super narrow if you don't want to be. Get out there and experience the world and other things if you are excited about that. Don't worry about making a flashy web app, unless you have a vision that requires a flashy web app to be executed upon. There are a lot of people in this world doing a lot of different things.
Anyways, it may be true that your ideas suck. Ideas can be big (usually they also require large teams for implementation) or small (and potentially growing from an existing need you have yourself or an observed need of a community -- e.g. no apps for cats on iOS). If you need an idea, observe a community, know a market, ask people more specific questions, then execute.
Do you need to make money? If so, how much? That's a good question to ask yourself now since there is often a tradeoff between coding for cash and pursuing other interesting problems (things like Project Euler certainly don't hurt either way).
However, potentially the most useful piece of advice I have for you is go social. I didn't do that myself until later in my career, but I found it helps tremendously. Find a project that you are excited about and start contributing code (even if it is a very minor way). Your code will get better much faster if other people are reading it and esp. if other people who know what good code looks like critique it. In fact, probably the folks who contribute to such projects will be more valuable critics than profs at Stanford or wherever else you end up (not that it isn't a bad idea to get a good education, but remember that's not all there is to the world).
Good luck!