Personally, I'm most excited about Gaul, at least from a gameplay perspective. Culture + Production seems like a powerful mix, as both of those are just so hard to come by in the early game. Also my biggest blind spot in Civ 6 is neglecting my defense and getting rushed in the classical, but I think having a warrior/spearman replacement along with an IZ that provides defense, will definitely be welcomed by players like me. What about you? Maybe Byzantium is more your style? Or what about trying Georgia out in the new Ages mode? Or maybe you have a favorite civ that you always use first with every update?