I think the path is really very straightforward. Assuming you're a developer, get a job, preferably with a local startup. Live really cheap. Work really hard, save %50 of your gross income. Do this for 6 months to a year and you won't need YC or TS funding.

In the evenings and weekends, build your idea.

If you've got funding to finish your university degree, then build your idea in your spare time and stay in school. Not as good, but a number of stratups have come out of college started projects (eg: napster, facebook.)

The really important thing is not so much your idea, but the skills that will come with trying to make your idea a success.

Trying to make it a success and totally failing is much more valuable than getting a job writing enterprise software or staying in school.

Assuming you're an engineer, and your idea is a web based one, you don't need money- you don't need investment-- what you need is living expenses. Get that covered and you're in a no lose situation. (Just make sure you have something to show for it if it fails- so that you can use the epxerience to get a job if you need one....)