Finally hit 70 a couple days ago and started the end game stuff. I still have no idea how to craft gems and such but I started the higher rifts and got a key to a greater rift. I did a couple more rifts but no additional keys dropped.... I guess they aren't guaranteed to drop which is annoying.

From what I have read the bounties are where you get the set pieces and rifts are for gems? I replace gear so quickly that I don't know if it's worth gemming anything.