This insures that no matter what, people will be able to tell who you are and how to reach you. Beyond the top two pages, do whatever makes sense for your group and your audience.
Every group is a little different, with different activities, kinds of people, etc.
Some groups of information will fit on one page. You only need one button for that, and the page can live in the main directory. Buttons for important stuff should be nearer to the top. Less important stuff generally belongs toward the bottom. Sometimes you will have something important that only makes sense in context, like Clinical Trials within the context of Research.