The hole size changes the width of the band. It is not directly correlated to ring size. So the hole size will determine the width only and that is more personal preference. I have been moving toward a more narrow band recently.
Another question to consider is what coins would you use? For a mans ring, half dollars and dollars seem to work best. Also, if your making a huge ring, size 17 or so, you may want a wider band width to begin with so this would be a smaller punch.
The most common men’s ring size is about a 10.5. For a half dollar, I would use an 9/16″ punch. for a dollar for this ring size, I would use a 11/16″. For bigger sized rings, I might go down a size or two, for smaller ring sizes, I might go up a hole size or two.
Quarters are pretty small to make but can be done. Size 8 is about max or you will start to loose detail. 7/16″ or 1/2″ on these.