I play Sergios quite differently than what is suggested, separate from the Byzantine empire at first. The main goal of this playstyle is to become a Greek Catholic powerhouse and eventually extend the ERE.
Starting moves:
1) Fabricate on Salerno. When you get this claim, go for Catanzaro (part of the Duke's demense, you want to weaken him so he is in constant civil war. Also is part of a 2 county duchy). Capua isn't worth fabricating on, as you can duchy-claim them.
2) Educate your son by a Catholic when he is born.
3) Your main goal at the start is to try to get the other barony in your county. It will double your strength. If you started out with a good enough arrest chance, go for that. If not, save about 110 gold for mercs and wait for step 4 to occur.
4) Look out for the heathens in Sicily joining any wars. If they join in the defense of someone, you can easily strike with mercs and take one of them out without intervention. Use your gold for mercs to take as many of them out before they can react. REMEMBER that the owner of Palermo is Shia, while the 1 county heretics are Sunni. They will call different allies and will not help each other out.
OR if Palermo attacks one of the smaller guys, make sure to war them as well and get to the siege first. With a ship, you will be able to get there first if you are watching carefully.
Mid game:
1) Keep pecking at Apulia whenever possible. Claim priority is the Duke's primary land until he has just 1 county and then your Greek land.
2) Form the Kingdom of Sicily ASAP. Once you take over the muslims in Sicily and press your two ducal claims, all you need is a single county to form it (Salerno, if you fabricated).
3) For marriages, focus on Croatia.
4) Plan your invasion of Africa carefully. They are segmented and are very easy to take over. What you have to be careful about is Mauretenia helping out. Offense is the best defense here, launch a massive campaign and don't stop until they are all subjugated.
5) Keep expanding until the first crusade is called. This is the reason for being Catholic. When it starts up, spend all of your money on mercs and head to Egypt, not Jerusalem. siege everything, especially the Caliph's personal land. Stay near the water for quick escape when the doomstacks come. The caliph will usually be busy doomstacking the catholics in Jerusalem though, so you will eventually destroy his reinforcements. As soon as you are King of Jerusalem, swear fealty to the Byzantines. Stay Catholic for the future crusades, though. You will have "recently conquered" on quite a large amount of your lands which is where the byzantines come in handy. Once you start getting troops from your African and Holy land holdings, you can choose whichever direction to expand.
