military missions pay quite well. so that is one route, promote people to serf and commoners means a lot of income, selling stuff like wine in a tavern gives you 100 gold per sale. Boar also gives more cash than berries etc. It builds up, look at what you can trade, sell stuff for even more cash.

So the advice boils down to, build, produce stuff for sale and expand.

How do you even afford this? I can almost build it, but the chapels for the amount of people i have eat up all my gold.
Can´t even dream of building more than a very basic church, let alone replacing the Chapels with Churches.