To help decide what menu items are required, it may be helpful to sketch out the groupings of top-level menu items (the ones that are always visible) submenus, sub-submenus etc. in a diagram form.

Below is a diagram for the example multi-level menu created step-by-step.

You can see how this diagram translates into a working menu at the bottom of this page.

Above is the finished menu which uses the same structure as the diagram. The finished menu was created using only one single menu placed on the page. See how it was created.