Getting ring sizes right is a challenge.  So an adjustable ring really helps as there is plenty of give. I've written about different adjustable wire ring tutorials before (see links below).  Here is another super one by Rena Klingenberg.

She uses 6/0 seed beads. But you could just as well use small 4 mm round gemstones or faceted crystals!

Before You Go:
Original Post by THE BEADING GEM
Jewelry Making Tips - Jewelry Business Tips