If you want to get Diamonds an easy way is to craft them using Ore, and along with collecting Ore, you sometimes get the chance of collecting a Diamonds. The best way/place to farm Ore is by going to the Basilica and then the Atheneum in Dragonspyre, then switch reams, just go down the whole list of realms you'll usually get at least 80 ore and and maybe two or three diamonds. Once you're done going down the list just start back up from the top.
