First I would say "No" the navigation bar is not the most important. Having a site that first, attracts your targeted niche and second keeps them there long enough to make the sale or point you are trying to convey. When it comes to navigation, Having a well organized design without a lot of clutter is important. You have a lot of choices and depending on the size of your site (how many pages) you may want to have drop down menus from a general category list. You also have the choice of having the navigation across the top (horizontal), on the right or left (vertical). Also having a site map is a good idea which should be a link at the bottom. This is the short answer i hope it helps,
