They should make a trading zone where you exchange money and food and steel/cement for diamonds, and you could like get 10 diamonds a day from this trade and you could only trade once a day. kinda like the respect thing and tribute and stuff.
Well, so far I have only played for 2 hours and I am lv 23 or so, I almost went bankrupt (financially) twice, I beat up my first lv 10 area, learned the importance of diamonds, and learned their cost.
I think that there should be a Inverted store, where you trade, for example, firearms for fuel, or such. that would be nice and stuff. con artists could decide what ratio it should be set to.
 "Falling Sands"){kind=icon}
 "Warfare 1944"){kind=icon}
 "The Godfather: Five Families"){kind=icon}
 "Warfare: 1917"){kind=icon}
 "The Last Stand: Dead Zone"){kind=icon}