I'm finishing up a CKII Jewish game. It is so much fun.
I had a 1066 start w/ the Khazars. I tried a 867 start a few times, but I was bumped out pretty quickly.
Holy moly is the game hard when you are the only one with a particular religion. I was beset on all sides by rulers of other religions. It was wicked tough.
However, that also made it interesting. Because marriage options to non-Jews were limited, I ended up building up a huge dynasty that intermarried with itself. That did mean that for almost all the time my count-level and higher vassals were of my dynasty. Which was nice for the diplomatic boost but also caused some trouble because nearly every body had a claim of some sort.
I started by moving up into Cumania and creating the Tartarian Empire (east of the Urals). Then I moved down into Alaina and Georgia (Eastern Turkey region) w/ a goal of getting to the Promised Land and building the Third Temple. I even made a merchant republic on the shores of the Black Sea to help with this.
Then the Mongols came along and really kicked my tail. They basically moved me out of Tartaria all together. I was worried that on losing my longest-held provinces I would be at a serious disadvantage. They managed to destroy my merchant republic and really press me. I had to move my capitol to central Georgia.
That forced me to keep moving further south into the rapidly disintegrating Muslim states. I had to pick and choose my wars carefully because my holy war CB would often cause my enemies to bring in allies. Plus I was under constant threat from the Byzantine Empire. I relied a lot on mercenaries, which meant trying to keep my gold up. I also heavily invested in horse archer armies.
I did try to convert the Tengri Mongols to Judaism but they went for Orthodoxy instead, which could have been really dangerous being sandwiched between two Orthodox Mongol hordes and the Byzantines.
Eventually, the initial two Mongol hordes ran out of steam. Almost right after the last invasion of them upon my people, several of the counties they took rebelled. To my surprise, they achieved independence from the Mongols. Their leaders were Jews of my dynasty so I was able to take them under my wing as vassals.
I was able to keep pushing further and further south until I reached the Levant. At that point, I had to engage in several holy wars w/ Pisa who had taken the Holy Land in a crusade. The Sunnis tried a Jihad against me, but I was able to turn it aside.
Around this time, a second merchant republic bizarrely sprung up on its own in Galilee. While my first merchant republic was planned and ended up w/ a pretty powerful trade network, this one hasn't gone anywhere. Very strangely, it is currently run (some 100 years after its creation) by a German Catholic ex-peasant leader. All but one of his stats are zeros. Very strange.
Almost immediately after liberating the Holy Land and forming the Kingdom of Israel, Tamburlaine showed up and started to punch me. I lost a duchy to him, but one of the counties flipped back to one of my vassals in what can only assume was a succession issue. I was very thankful for this b/c I knew they would attack that one county next time, rather than going after bigger game. I need not have worried, once the truce ran out and they declared war on me again I was able to defeat them and retain the county. This stopped the Timurds from attacking me again as I think they then ran out of steam.
Then I got hit w/ a crusade against the Holy Land. This attack was tough to defend against, but I managed w/ some fancy footwork.
As I write this, my game is nearing the 15th century and I control Alaina, Georgia, nearly all of Mesopotamia, Israel, and a sizeable chunk of the Turkish interior. I was able to rebuild the Temple and recreate the Kingdom of Israel.
As the game winds into the late years towards its end, a Jewish adventurer from my dynasty just showed up w/ a goal to reclaim the duchy of Itil, on the north shore of the Caspian, from the Timurids. That was my initial duchy. I am going to offer to join his war and help him push back the Mongols.
Update: Just after joining the adventurer's war, another adventurer popped up to press his claim against the Zealots, the Jewish holy mercenary order. Which is kind of bizarre.