What I do is : first off, ally with the Pope, and get him to love you (which is easy enough). That will make the Christian factions very hesitant to attack you, and if they do, their generals are quickly going to become little smoldering piles of ashes. I also try and make as many alliances with your neighbours as you can, not so much to dissuade them from invading me out of our alliance, but to make any would-be invader believe that he's going to get ganged up on if he tries.

Then I turn everything in the Venice area into a city : Zagreb because I want its population to rise quickly to build mines and roads there ASAP, and the provinces around the adriatic because, well, they're shore provinces, which means they deserve their 3 oversea trade routes each. Besides, Italian militias are very good at what they do, and much better than early castle infantry. Plus if you manage to secure a Merchant Guild, you get Merchant Cavalry which you can use as budget knights... meaning I really don't need any castles early on. That will probably change when footknights appear, but until then, I'm good.

I then build a powerful navy, train it against pirates, conquer Crete, Rhodes Izmir first, then Izmir if there are still rebels there, and turn them all into cities. With those 7 provinces, I can generate an amazing amount of cash as long as I have trade agreements with Byzantium, Milan and Sicily and don't attack them - and they usually don't attack me.
Milan will try and invade southern France or the HRE, Byzantium is of course bogged by either the Turks or Hungary. Sicily is a toss-up, but you can pretty much deny them any opportunity for attack with a strong navy. With that cash, I can tech up ultra fast while waiting for the First Crusade.


When the Crusade is called, I have my heir (and always him - that way, he'll benefit from the huge stat boost a general gets when he successfully leads a crusade, meaning when his dad dies and he rises to power, he'll boost my economy even more) hire 8 mercenary units, join the crusade, buy some more crusade-only mercs around Venice, hop in boats and move towards Antioch by sea, joining with my by-then very experienced navies on the way. A powerfull 10-12 boats fleet is enough to fend off both pirates and the egyptian navy should they come my way. Reaching Antioch, again I'll buy every crusade-only mercs I find there (I have a soft spot for the Big Towed Cross ;) ), assault the city and take it, usually without much resistance. And now, all there remains is mopping up however you want to - defending Antioch from the Muslims is easy, and with the trade/farm/port infrastructures I've been building all along, the Venice-Antioch trade by itself is ungodly. Coupled with the cash experimented merchants can make when they're on ressources from the Levant, well... let's just say the sinews of war won't be much of a problem anymore