My experience has been something like oldephriam.
Find a small jeweler that will work with you. Maybe one that is just starting
out, that has some talent.
I have done this three times for myself and once for a friend.
The first time I provided the diamonds, mostly from my metal detecting finds,
My wife and I worked up a design and the jeweler made the rings just liked
we wanted. I think we had 3 or 4 hundred into the two ring, but that was
30 years ago.
Last year I had a 1.3 caret diamond,,another metal detecting find.
I went to a jeweler that was working out of a local coin shop.
He had catalogs of rings that we could look through. We picked a
white gold Tiffany setting with the right setting for the diamond.
Here is the ring with the diamond just sitting on top.

We had this ring made for less than $500. But we did have the diamond.
I am sure you could find a jeweler that would use
your gold, but I do know they like to start out with
.999 fine gold.
The big part of rings like this is the diamonds.
If you don't have your own diamonds, you need
To find the wholesalers in your area and see if
they would work with you.
I know this can be done, and you will save over 50%
versus buying at the big jewelry stores.