in my ptolie game (yeah here are people playing them!) core of my economy are the rich towns in the levante (tarsos, antioch, side and salamis). you could may conquer kophen (or do you already got it, its near north-east of india) it is very valuable mines which are at least necessary to play as baktria. your prob is the really too low income, no too high expenditures. are you at war with the faction controling athens? since many sea routes go there rhis is really a loss of wealth. war doesnt only costs armies, but really decreases income! i had to feel this when starting my invasion of greece as ptolie... suddenly my income decreased steeply by 10 or something k mnai PER TURN. so maybe settling peace would be another way. i may could check the finances in my ptolie game tomorrow ( there i am swimming in money with a smaller empire and definetely higerh army upkeep.