TOP RANK ONLY, THE REST ARE A VENDOR PURCHASE
Realm
Region
Class
Platform
How it is delivered
Lower-rank gems are an ordinary vendor purchase for a trivial amount of gold. Selling them would be selling you something you can buy yourself in thirty seconds. Every row on this page is the top rank, which is the only one that takes real farming.
Rubies are life, sapphires are resistance, emeralds are critical damage, topazes are armour and skulls are armour and healing. If you are not sure which your build wants, the coaching hour covers it, and it is a cheaper answer than socketing the wrong set.