A couple of free tips for all the newbies . I'm not going to write a general economy guide, the principle is the same as in Stainless Steel. I'm going to focus on merchants. As you may have noticed, merchants are no longer the useless clutter they were before. In this mod they are extremely profitable and, if used to full potential, can even become your biggest source of income. In my current Roman campaign, I receive over 50.000 florins per turn from merchant income alone, which is even more than I receive from taxes and represents one third of my total income. In more practical terms, merchants provide almost 50% of my military budget. Not bad, eh?
There are two main things you need to know: how to get high-level merchants and where to send them.
Step one: There are three variables that determine the starting level of a newly trained merchant: The level of a market in the city, the presence of a merchant's guild and random luck. Instead of just producing merchants where you can, I recommend that you limit their recruitment to a single city, the one with a high level market and a port (i.e. your factions biggest moneymaking city). The best examples are: Constantinople, Italian coastal cities, Alexandria, Jerusalem, Antioch, London... After a few turns, when you've accumulated enough points, you'll receive an offer for a merchant's guild in that city. A merchant's guild, in addition to increasing your city's trade income, provides positive traits for your newly trained merchants. But there is also an element of luck involved, so from time to time, even with high level infrastructure, you'll get terrible merchants. If that happens, simply send them on a "suicide takeover mission" against other factions merchants (the amount of merchants is limited to how many markets you have). Merchants' skills can also be increased by accepting "Great Trade Fair" events, by successfully acquiring rival merchants or by positioning them on resources.
Step two: The amount of income you receive is determined by the value of resources, by distance from capital (more is better) and also if you have trade rights with the owner of the region. So it is best to send your merchants outside your borders and look for gold, cotton, silver, pepper, silk, slaves and others.
The two best locations (that I've found) are gold mines in Upper Hungary:
and in Carmania (the south-eastern edge of the map):
some other profitable locations:
gold in Serbia:
cotton in Nile Delta:
gold in Armenia:
silver in Transylvania:
Other good locations: gold in Tunis, Upper Egypt, south-eastern Arabia and Novgorod, silver in Frankfurt, Trebizond, Malatya, Tabriz, Sardinia, Bosnia, Granada and Toledo, cotton in Pisa, Aleppo and Basra, pepper in Venice, Pisa, Antioch, Acre, Fes, Carmania and Basra, slaves in Pereyaslav, Crimea, Dnieper Lowland, Genoa, Ani, Libya, Upper Egypt and Tunis and silk in Constantinople, Damascus, Crimea, Sicily and southern Spain.