Dacia in the north, Carthage in the south if the map is all I have to go on. They seem to offer expansion without being too far from the capital.

But in practice I would expand where my armies and enemies are.

Sounds like loads of town control measures are needed to stop rebellion. If you loose a town to rebels/enemy then exterminate it on recapture.

By now you will have played on? What did you do ?