When you are considering how to monetize your site, try to think about how your site will appear from the point of view of the users. The chances are that as a user, you don't enjoy sites with large amounts of advertisements. You may also be turned off by sites that constantly promote merchandise or try to get you to pay for features.
In the early days of building a community, it is important to encourage members to be active and to promote the site to their friends. As your traffic grows, you can start offering paid-for upgrades, subscriptions, and ad-free surfing.
If you plan to make a feature premium, make sure that it's something that would be "nice to have", but isn't essential to using the site. One example would be RSS feeds. Some sites allow anyone to visit and browse through the site's latest additions but offer RSS only to premium members.