Not a given to determine how as it is not as straightforward as it might be thought of. I notice for example that taking a city from a faction does influence the wealth of some of the faction's left cities. If a city occupies a key location relatively to other kingdoms and production centers, it will grow rich. If a city has secured trade routes to key products then it becomes a hub for trading. Wealth of cities looks like it is mostly reliant on trade and therefore on location at a given time.
My belief is at present times, the map lives (mostly)by itself (regarding to this point) and the wealth of the different cities results from how the map is shaping with an invisible network being woven and determining the wealth of cities. If you can try to influence of course as for caravans or bandits, your actions seem bereft of any consequences. If you act according to the advice given by the guildmaster, you will find out you have little influence on what is happening. I dont think you exert control on that point at present version.
