Hi, sorry for the late reply. I was in Cuba and the internet connection was rather bad.
For jewelry, 99% of the stuff which is sold in stores in Cuba is made of common metals. They sell many “gold color” jewelry, but it has no gold in it. These items sell for like 1$ to 2$. Most Cubans wear these kinds of things. They look pretty, but have no value.
Some upscale stores sell gold plated jewelry. The prices are high and the actual value of the jewelry is very low.
As far as I know, there is almost no real 14k or 18k gold being sold in Cuba. If there is some for sale, it will probably be very expensive – far more than the value of the gold.
Most of the Cubans with actual gold have long since sold it and taken the money to buy other things, or taken the money out of Cuba. Any gold you find for sale in Cuba is probably imported from the USA and as such would be priced at a considerable markup.