I noticed one key thing in this Danish GA campaign was keeping a balance of farming and trade was important.

Why you may ask? Because at the expert level, the AI factions are much more likely to disrupt your trade if they see you becoming too properous. They often might only sink one ship, but if their navy is as widespread as yours, it will disrupt trade for a number of turns (sometimes as long as 35 yearsas in my campaign).

This is when savings are important and you can combat the disruption in trade in a number of ways. I did a combination of increased farming (to bring in other income) as well as quickly of course trying to sink th enemy navy. I was fortunate through most of the game that I had a superior navy. I didn't earlier on, but then no one saw me as much of a threat.

Another option is to attack, and then of course you must hope that they are a faction not protected by the Pope. This can cause you to keep picking new targets for income razers or jut simply grabbing money when you disturb the peace, as I often did at certain stages in the game. Generally I did this when I was provoked or when I saw an opportunity to pick up a province I wanted for border or trade purposes.

One thing I never did was take Scotland or Ireland. I often see Ireland as isolated (I'm not big on picking up the island provinces, sometimes troops get stranded) as well as I didn't see a good reason to pick up rebellious Scotland with its minimal income. I suppose the highlanders would have come in handy in desert battles, but the vikes did okay for me, so I didn't feel I missed out on much by not taking either one.

Speaking of income, one thing I often did was cherry pick provinces based on their trade incomes and locations relative to what I held. One risky thing I did was taking Constanople and Greece later in the game (after the horde had faded, would have been much more daring earlier). I wasn't as close to their locations as I would have liked with the rest of my empire, being 3 to 4 provinces away. Interestingly, I never did get a direct land connection with them (well perhaps briefly when some intervening provinces rebelled for a turn), but the opportunity to take them both was too big to turn down.

Often too, taking away a big income earner is a deal breaker for another faction, as even if you can't always get much income from the province yourself or even later lose it, the other faction may experience hard times and suddenly lose loyalty in some other provinces if you cut one of their main economic bloodlines.

Of course you may take provinces for troop building, but I generally didn't find that was the main reason for me to grab provinces in this campaign. I simply looked at the map, and if the opportunity arose and a province was not too removed from my other provinces and had decent trading items as well as being a coastal province, I took it. The only good provinces I missed out on were on the Italian pennisula and Egypt. For much of the game, the Italians (or at one time the Sicilians) and I were not at war, so I didn't risk losing the trade income as well as being concerned with being stranded on the end of the pennisula below the Pope. Egypt on the other hand, I often wanted to take it, but the right opportunity never presented it (and later I was too busy fighting in the heart of Europe with the Hungarians to bother much with the Alomonds who were very bottled up with trying to crusade to Syria).

All and all, quite the entertaining campaign.