Sounds good, I'm about 50 years into an AS campaign atm using a simmilar method to your own. Personally I gifted/let rebel more or less everything east of Persepolis, and have only just retaken my old provinces. Same as yourself I'm only just getting involved in Anatolia. Ptolies are beaten back to the sahara and the lower nile and have been at peace for a few decades now.
My advice would be continue developing your principle cities, and then just develop any infrastructure where you can, preferably on the interior of your empire (unless you have some really productive border provinces you want to develop).
Then just cut costs by keeping garrisons to a minimum, keep a few small armies of regionals and mid level troops to defend your empire, and use your developed cities to pump out a "proper" army or too.
More or less what I did anyway and seems to have worked quite well so far
Cheers
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