I like Sicily, nice and simple to start with, loads of options! I have found that a bit of conquest in North Africa (Tunisia/Cyrenacia and then on to Egypt) coupled with lots of crusading (thus hitting the Egyptians from two fronts) can quickly give you the southern and eastern Mediterranean provinces, lots of ships and a nice line in trading. Sicily is probably the best placed crusading faction; it's only a short sea hop from Malta to Outremer, you need lots of ships anyway, and your income will be mainly trade-based at first.
Snatch Naples if you want, probably better to wait and see if it revolts and then take it from the rebels rather than directly from the Byz, cos you can trade with them and having them sink your ships mid-crusade is very annoying. Same with Rhodes, Crete and Malta; cut them off with ships and snatch them if they rebel. If you think your empire's up to it, kick off with the Byz full on and grab Greece and Constantinople asap, preferably while the Byz are fighting the Turks or Hungarians. I have yet to take a Sicilian game all the way to the endgame, but smacking the Italians about seems logical, they're going to be your main competitors later on. Keep building ships though, all the time, and use lots of mercs as well so you can drop an instant army on anyone who deserves it.
It's probably unwise to attack the Pope though, you need him friendly. Eventually the Italians will probably attack him and get ex-comm'd, at which point you can righteously bury them.

Good luck, I shall follow with interest however you do it...