Starting with Byz's

[Weebeast]

Take Rum as it's the richest land compared to the other two. As you begin, just stack all troops in Trebizond and attack in second or third turn.

You can instead take on rebels in the balkan but that's not good as either one of those muslims will be so big once one is wiped out.

Look after Naples. Sicilians are gonna invade that soon ( Naples or Greece, depends).