1st way:

It is worth noting in Fast Dial that there is a sort option for the cells that has existed for a long time that cells can be sorted to show the most visited sites.

right click on fast dial page, chose sort and then visited:

2nd way:

As well as the above it can be noted that if one goes to Firefox Bookmarks/Orangise Bookmarks that it is possible with the right click context menu to select Fast Dial Make Home.
Using this feature it is quite a simple matter to chose for example to chose the most visited folder.
If that bookmarks folder is selected one is in the most visited folder of Bookmarks. So it is under bookmarks control.
If one wishes to return to the Fast Dial folder then right click on the Fast Dial folder in Bookmarks (in bookmarks menu) and make that Folder Home.
Once that is done all the stored cells and logos of your personalized Fast Dial will reappear.

Most Visited Folder in Fast Dial: