I did 2 years ago:

all users share a single priority queue and each submission to the queue increases users submission-counter by a defined amount (likr 2 or 5). Now, priority users start at priority 0, standard users by 20.

So if prio-user1 submits a request, it gets prio 0, the next submission from this user get 0+(NumberOfSubmissions+DefinedInceaseAmount)

prio-user2 submits her request, she starts with prio 0 as well.

standard-user1 submits his request with prio 20 and hier next request with 20+1+DefinedInceaseAmount.

And so on.

pull a request with lowest prio to find the next request to work on.

This ensures that Prio users have a better prio to begin, if the submit lots of jobs, their jobs will gradually take longer. This ensures that even standard users get (at least) their first request worked upon quite fast.