A couple tips of my own that may help you in future campaigns:
- As I play the HRE a lot, I know what it's like to be surrounded by potential enemies. The best way to deal with that is decide which directions you do and do not wish to expand in. Then start making alliances based on that right away. It is absolutely vital that you immediately strive to cement alliances. If you have ANY princesses, this early in the game they are best used for marriage alliances. None of my marriage alliances have been broken. That said, you still need to do some work to keep the marriage alliance from deteriorating (as with any alliance), so the occasional 1,000 florins or so will go a long way. Doing this will give you safe haven on the fronts you won't be committing your troops to, and that is a huge relief.
- If you do decide you want Sicily, keep a few things in mind. Firstly, Norman Knights, as I said before, are monsters. They are Sicily's shining star and they dominate the early-mid game. Simply put, they are the best infantry/cavalry until Citadel-level and, due to the AI's scaling in battle, they will tear even general's bodyguards to shreds. Also, Sicily almost never does anything but sit on their wealth, so they're always ready to create/spawn huge stacks of armies. Fighting on their land will be painful. The only way I know to take on Sicily is to take trebuchets with you on a boat and take Palermo in one turn. Without Palermo, they cannot get any more Norman Knights, and your invasion will be a LOT easier.
- And, as stated elsewhere, you simply must control the great Italian cities. And then get trade agreements to really suck every penny you can out of them. Thankfully, since you're Genoa, you shouldn't have any trouble garrisoning the cities, so you have an advantage there. Oh, and kick Venice out of Italy. I believe they're your biggest rivals, and you should just let Asia deal with them.