Adding further content to your website is simple. Information can get more complex and you can put your point across in more detail. Use your inner pages wisely to build up your content.
Secondary navigation, and even tertiary navigation, can add layers of information to your website. Hit the visitor with some overarching information on the homepage as a catch all, and then allow your customers to delve as deep as they want to into your site.
You can add to the levels of complexity the further people journey around your site. But don't overdo it - content hidden away is less likely to be found, and won't provide for a great user experience, and you could be missing getting some key information across.
Three clicks to every piece of information is pretty good practice, but if your site has thousans of pages, that might not be so easy. Make sure to spread your information out, and always consider your site's architecture.