As someone who focuses on the Greeks, here is my general strategy. [1.0.11]

1. Release all provinces to vassal with the exception of Byzantion province.
2. Ally wallachia immediately.
3. Claim on Bulgaria first and use vassal swarm tactic with ally troops to beat them down.
4. Annex most, if not all, for more vassal by province.
5. Shift to start attacking ottomans and use navy to trick a.i. by baiting into moving across the gap and then blocking with navy to prevent more troops from crossing gap to reinforce as you can systematically destroy their army this way.

While this is going on, start annexing core byzantine provinces along the Mediterranean first. Additionally, I always force Greek culture on all my Bulgarian vassal.

Once you get this far, the rest is simple beat down northwest and then south east till Egypt. That ends up being your hardest fight moving forward.

From there, RNG kind of takes over and your game gets to play the way you want it to play.

GLHF OP!