Since this isn't really a guide or an AAR, I'm moving it to the main forum.

New member cannot post links until they've posted a few messages. This makes it harder for spambots to slip through.

As for your question: I'd conquer Egypt as soon as possible. It's an extremely rich territory, and the Ptolemeans are likely to waste all that money by throwing army after army at you. Since you are already at war with them, I see no need to pick another fight.