I can never play tall for some reason. I just get bored too quickly since it feels like I'm doing nothing except waiting for my gold to tick up for upgrades. Maybe I'm doing it wrong?
If you haven't yet, you should try playing as a loyalist Kingdom within an Empire and being completely loyal. Empire declares war? Always "Offer to join war." Empire civil war? Always take the side of the Emperor.
Imperial Dynasty dies out or gets deposed?
Game over.
A really fucking fun run.
It's really easy if you are the head of faith of a large religion with the communion tenet. Followers will throw 100 gold at you every few days.
Reform your culture early to take the tradition that boosts development on the terrain where your culture is located (this was drylands and desert for Hausaland/ Hassan culture, the respective perk boosts the development growth for Hausa counties located on drylands by 30%). Get the collective lands tradition also later to get a further development boost if you can find a convenient way to do so, either by giving land to peasent leaders you put down as this will give you a big prestige discount for adopting it, or just save a huge amount of prestige to get it without the discount. I took the city keepers tradition by hybridising with one of the neighbour cultures, allowing me to build the guild line of buildings in my cultures city holdings an era early, these also boost dev growth. The Hausa culture also starts with parochialism tradition which buffs cities from the get go, so you build as many cities as you can in your cultures territory and then build guilds within them, and also trade ports too for any ones that touch a body of water or river (for Hausaland this was only 2 counties to the west of the capital that touched a river).
Another huge boost is the megalithic construction tenet if you reform you faith, letting you build megaliths in your temples which, you guessed it, boost dev growth. You can build a LOT of these though and there is no technology prohibiting the higher tiers from being built early. You'll want to lean hard in to constructing temples instead of cities if you go this routez I didn't this time because the starting culture just favoured cities so much.
Always have your steward working on increasing the development of the County of your culture with the lowest development. The way development spreads means its more convenient to move him around to the lowest developed counties often instead of making him pump up your capital all the time, there is a threshold where growth will suffer if it's too high too early.
Do all this without expanding much bigger than a kingdom or small empire, focus on stewardship tree + the few learning tree perks that boost dev growth and soon you will be making excess gold even without communion. The wait for the technologies that unlock the next tiers of buildings will be the main thing holding you back then.
Tldr: Min/max in to development growth with traditions and buildings and keep your steward working. You want to be the yellowest Kingdom on the map, knock the Romans and the Greek Romans off their high horses.