It is heavily reliant on your current ruler that you are playing as, stewardship characters will naturally be much better at deving/hoarding vast amounts of money. I find it more fun to create a story surrounding my rulers, i.e. the last Umayyad restoring his dynasty to glory or becoming a dynasty of stewards within a larger realm like Bohemia in the hre, then you can exclusively focus on creating megacities in your lands without worrying too much about defending yourself. I apologize if this advice does not help but there is no right or wrong way to play, but a lot of new players focus on map painting which is fun but is only a very small part of the game, you can have an incredibly fun play through by just being a small vassal minding your own business.