you are right this is very hard, i tried with different settings on manual and it was a guessing game till i was able to get something. I then had to go into photoshop and fix the images to get something somewhat decent.
btw, i used an led flashlight above the ring at different angles till i was able to get some sparkle but it is hard.
Do you have Lightroom or photoshop?
Model: Canon EOS 5D Mark II
Exposure: 1/20 sec
Focal Length: 50mm