The closest to a functioning plutocracy you might find would be the merchant republics of medieval Italy. There, various families found massive success via trade networks that led to outside of Europe. This led to generational wealth that was used to buy influence in local politics. Before long, these powerful families were directly running the government and using the government to further their own wealth. Some common traits of these republics would be:
  • Three levels of politics: politics within the family, politics within the city-state, and politics/diplomacy with outside powers. Political rivals could arise from any of these areas.
  • Political assassinations, especially by poisoning
  • Public works to build the prestige and influence of families as well as to get citizens on their side
  • Humiliating rivals publicly, especially at festivals, parties, and other large gatherings
  • Rarely, open violence in the streets between factions
  • More rarely, alignment of rich families with outside powers to attack the city by force

You can view the Capulets and Montagues from Romeo and Juliet as being such families. Also, take influence from the Godfather movies or other pop culture about the mafia. You might also get inspiration from Westerns where there is a wealthy land-owner or powerful gang that comes into conflict with another one (like Tombstone).

Such games are well-suited to intrigue and deception.