Gem cuts have the largest profit
Jewel-crafting also requires some rare recipes but even without it, you can make some decent gold. We used to farm adamantine / fel iron to prospect, but now we just buy kal online geons. In fact, we prospect all our ore and open up our JC profession window and checkmark. We head over to the Auction House and then check which gem cuts have the largest profit or the one there are few or none of on the AH. We make 5 of each jewel based on 1/2, until all our gems are gone.