Hiya, just adding my two cents here.

I played on Medium for both parts of the game and played a short game with England where the end goal was destroying the French. Since it is on Medium you can often get away with some things that in a harder game would be suicidal.

Anyway, like others stated, I concentrated on the main isles first. I left Nottingham as a military city as well as Caen but all other cities I turned into villages. I concentrated on the Scots last after taking out all other rebel factions. I never ransacked or exterminated the population on the main islands but instead just occupied the settlements.

By about turn 20, the Pope calls for a Crusade. I had one general who I didn't like much so I sent him on the Crusade with a small army. To my surprise, he made it to Jerusaleum in only one boat and so after getting a few more units attached to him the little army took the city. But, having them just sit there wasn't helping me much so I abandoned the city and turned south thinking I could go west across Africa and take some more cities now that the Army was quite large and even the Pilgrim units were seasoned veterans.

I found that sacking Cairo and Alexandria is very profitable making about 40000 gold off those two cities, money which I used to upgrade all of my provinces.
A little later another Crusade started and it went to Antioch. I took that same Army up there and then tried to sail them home because by this time the general was getting old. But, their ships were attacked and sunk.

As for the French I took some of their territories but the Pope kept telling me to stop. During those times I would just shift units and rebuild. By about turn 50, Denmark and Milan also posed a threat. They would attack me but I could normally stave them off easily enough allowing me to focus more units on France.

By about turn 70 the French were gone so now I might restart and try a larger campaign.