Each of my Favorite Stories is a story that I enjoyed reading overall. So if you’re looking for something to read, I recommend that you sort by Status to see completed stories, then use Ctrl-F/Command-F to search for the name of a fandom you like. This will lead to all of its completed stories in my list. Or you might try just browsing the whole list and picking a story with an interesting description.
Even though my Favorites list is long, I don’t favorite stories indiscriminately. As you can see on my Communities tab, I have a community “Rory’s semifavorites”, which is where I put stories that I liked some parts of a lot, but that also have significant flaws. If you exhaust my Favorite Stories (not likely!), you could try filtering the stories in that Community and see if there’s a story there whose bad parts you won’t mind as much.
Be warned, FanFiction.Net is buggy: if you try to sort my Favorites list by Status or any other criterion, the page displays only two-thirds of the stories on the list. So if you sort by something and then don’t see the story you’re looking for, my list may still have it. To see all completed stories in my list, refresh the page, then press Ctrl-F/Command-F and search for “Complete”.