Also a good point by the Glorious, I make a killing selling all the uncut gems I don't use from leveling.
I mean, when I was trying to get Citrines back in the day and ended up with 2 stacks of Jade instead, it turned out helping to pay for the ore.
Side note: If you get lucky with your prospecting, and get 2 or even 3 gems from 5 ore, then you can get a nice little racket of buying ore then selling the uncut gems.