Gold coin rings can be pains if a person isn't careful. If you aren't gathering together with people carrying gold verified detectors, buy a couple of fake gold coins from alibaba as any gold/gold plated coin will scratch and damage easily. If a person wants a "coin " ring that will eventually be damaged, buy one of these. IMO, Jim https://www.shandonscoinrings.com/
Using a California gold token would be a bit expensive unless you use a charm and the charms are normally not real gold. The one in the pic is 20k in a 14k bezel, it's the real deal but like I said, no doubt hundreds of dollars. Maybe a fanam would go well in a ring as they don't cost that much!
A half-sovereign is an attractive coin. 22k, 0.1176 OzT in gold. It would probably run at or just under half of your budget. It might be a little big for a pinky depending on what you're after. I'm not really a jewelry person so I don't know. If you want REALLY small, maybe look at a Canadian 1-gram maple leaf? They are 24k so more susceptible to damage, but they're so small that the material around it would likely protect against getting banged against things.
