I am a web application developer, have developed a lot of sites, portal and apps for clients. Now I want to have own such sites that with which I can do business. But I don't know what are steps to do so. What I know is make a site or portal. But what after that? There are lot of people having so much traffic on sites built with some simple open source. Many of them are forums. I also wanted to start a forum and a web portal. I can develop that or can have open source. But what after that? Content entry and SEO? Is it all to promote a portal or site? Do SEO nowadays work ? or it is all about marketing and advertising? I have no idea about that so please tell what you guys suggest.

thanks for every one's opinion in advance.