I have a good idea for a website?

[Zarn]

You would usually make a low-fidelity prototype, and then go shopping for technologies that can implement the functionality you want. Premade or bundled is much cheaper than bespoke, if you can't make it yourself. Looking for a good designer is a combination of ads, word of mouth, and google.

Buying ads on Google is a good way to route traffic to your website. After a while, you should have your website crawled - and if you get others to spread the website, for instance through Facebook, Twitter and other social media, you should get traffic.

Let me rephrase the last question - how did YOU discover the newest premium website that you were interested in?