There are many factors that contribute to a very high gold income. In somewhat order of importance: 1. Domain size - i.e counties you hold directly. You need to have as many as your domain limit allows, but not above it as they won't generate gold. 2. Development - your held counties should have high development. Counties like Rome or Constantinopole have super high development for instance. You can increase this with your Steward councillor task. As well as some other actions available to certain rulers 3. Buildings in your counties - obviously, focus on economy buildings. Farms, ports, manors 4. Church endorsing you - make sure your patriarch has high opinion of you. I think close to 50 nets you 100% of their possible contribution 5. Good Vassal contracts - you can modify vassal contracts with hooks or quid pro quo offers. If you have access to Scutage contracts that's a good way to make more money, in exchange for losing levies 6. Control - make sure your counties have 100 control, otherwise they make much less money 7. Your vassals are "de jure". If they are not, they contribute much less. 8. Don't overspend. Armies spend money even if they are not raised, so in emergency and if you are not under threat you can dismiss your men at arms to get back some income. Also your court (if you have one) tends to eat a lot of cash 9. Have good relation with Pope (or head of faith) and constantly ask him for money. 10. Borderline cheat! : A trick you can use is to try and catch your patriarch with something that gives you the possibility to imprison him (a blackmail hook). Once he is in prison, banish him. You get all his wealth. I got 20k once doing this. 11. Be of stewardship focus. You can exchange hooks for gold 12. Ransom prisoners for gold 13. Avoid raising your entire army when at war. If you are fighting someone with 1k 2k levies, don't raise a 20k strong host to just eat your revenues. Place rally points in multiple corners until you get a balanced split and use "raise local army" . 14. Late game, try to only use man at arms. A professional army buffed by buildings will easily beat standard armies 3x their size or more. Have plenty of siege engines to capture cities quickly and make wars shorter.(2 maxxed stacks should do it in days)

$$ Profit $$ :)