Hi! You missed two expansions; Rise of the Bloodborn and Ancient Bonds. Both are mini expansions, they have roughly 50ish card in each set and work differently than Shim'Zar. Each orb is 300 gold but each orb gets you a playable set of 1 of the commons, 1 of rares, and either 1 of the epics or legendaries. Once you get a set you cannot get any duplicates.
Rise of the Bloodborn introduced Blood Surge, pretty much abilities that proc off BBS triggers.
Ancient Bonds introduced support for Arcansyts and Golems. All factions were divided between the two. Songhai, Abyssian, and Vanar are Arcanysts and Vetruvian, Lynor, and Magmar are Golems. The expansion released Bond, pretty much effects that trigger when a minion comes into play as long as a member of the same tribe is on the field.
We recently got a major nerf so not sure about the meta right now. But currently Arcanyst Faie and Midrange Magmar are considered top tier.