Starting from “an idea” you need the technical person (maybe just one at first) to help bring your idea to a physical state. In the computer world, that means “coding”. Creating the database to store the information to be captured by the website, whether that’s for orders and sales (like Amazon and others) or users and personal data (like Facebook) or searches and website URLs (like Google and others). Your idea is brought to life via code. (And that database of goods and prices and suppliers, or personal information, names and addresses of clients, etc. – that database is gold to you. You have to treat it that way. You even have to consider how you protect it from some of the people who will be working in it day after day.)
So you need a database expert (and later a database administrator, analysts, etc.) and you need an HTML expert. Again, for the prototyping and modeling these could perhaps be the same person. Considering the value of your database, you definitely need a security team.
Once your idea seems at all feasible, and you have ideas – even if they’re still untried yet – about where the money will come from, then you can start to beta test the idea. You may still not be “online” yet; you might do all of your testing in a closed system that only resembles the Internet, but now you need testers and probably more database people.
Later on you’ll probably go online for real, but without a lot of fanfare. You’ll still be working out bugs and finding and plugging security holes – there are always security holes. You might start testing the water in taking real orders, making real sales, attracting real customers and advertisers, but at great discounts, because you still need to find how to deliver service, answer “help” questions efficiently (and start building your FAQ database, and setting polices which you’ll also have to codify), and you’ll always be looking for more cash to pay the people who are doing all of this for you. You’ll be working late nights and early mornings, seven days a week, and probably maxed out on your credit cards and tapped out with all the borrowing you can do among friends and family.
If the idea is still working, and if you can scrape together enough equipment (including servers and web hosting services, especially), then you might make some kind of modest invitation to a select group of people (either people whom you assume would be interested because of expressed preferences in online groups, or people in a local geographic area, or the like) and “go live” among them. You’ll find and fix more problems than you had ever considered before.
Someday, assuming you’re still alive and interested in the idea, you will absolutely need a lot more cash just to keep it going, as well as to grow it. So you’ll have to pitch the idea (that is, “sell it”, not “throw it out” – although the parallels are apt) to venture capitalists who will be willing to give you the huge cash infusion you need, for a piece of the pie.
Either that, or you sell the whole thing, as-is, to someone or some group who has also been sold on your idea, and you… may be thoroughly sick and tired of it by now.