Today I got around to trying the CK2 Demo. Pretty fun, I have to say. Played as the duke of Adrianople and Vidin, and became Roman Emperor within a couple years. I inherited a war with the Turks, which I won, but had to end because I wasn't getting any reinforcements and the Turks were (lesson 1 in mechanics). That proved to be a hazard as without the +30 Fighting Infidel modifier and outside threat, my vassals started rebelling like hotcakes, and my younger brother Andronikus was kind enough to make a ploy for the throne. Good old Byzantine instability, just like it often was back then.
The outcome of the war was in some doubt for awhile, but I was learning the mechanics and was able to get a White Peace in the civil war, imprison some of the disloyal vassals, and white peace with the lucky ones. Of course, that meant my brother was still trying to assassinate me, but he wasn't better than my guards, and before long both of my brothers were imprisoned and stability was restored. That gave me enough time to conquer Tripoli and start a conquest of Aleppo and what I didn't own of Mesopotamia before the demo ended, as well as exploring some of the non-war options in more detail.
So I think it's decided that I'll pick up the base game. My question is, which expansions are great, and do you have to get the first one to get the second one, etc.? I'm thinking that the Old Gods looks pretty cool since I'd been hoping to play as a Norse religion (although I'd like to do that in 1066 - not sure if it allows that?), probably Sword of Islam, and definitely Sunset Invasion for the third or fourth game (although I'm not sure I'd want to always have the Aztecs invading). Legacy of Rome, maybe, I had fun with 1.00 Demo as Byzantium. Republic, I don't know. Also, in which expansions can you play as the Golden Horde once they come to Europe?