I'd like to say that once you do see the queue, that unless you want to see it again, I recommend using single riders, especially with Gringotts. Even if it's early morning, or late evening.
As that line typically Gringotts a long wait and can be partially outside. Sometimes even when it comes to a 30 minute wait, which isn't too bad at all. Also, the single rider line frequently fills up quickly (especially on that ride). So, while it can seem not that much of a wait, just save yourself a little time with going through the single rider line. As it is often shorter of a walk. So while it says "5 minute wait time" for the regular queue and it doesn't seem much, it often feels as if you're literally walking for that long, or even longer, so to save yourself even more time in the future, it's good to use single riders even when wait times are low. In the time you're walking through the whole queue to get to the ride, you could be half way through the ride already if you do the single rider line (especially if there's not that many people, or no one in front of you).
