To increase gold, you have to increase population. You can also research gold increasing techniques. This post documents the population gain from each building type.
Note1: Second number in () is if you built an aqueduct for the 25% population bonus in (only) your first city.
One oddity is when my aqueduct was finished, the population rose 23%.Some results are surprising. Cottages are for population but storehouses and warehouses will be better for population until you can build apartments (because storehouse can be higher level in feudal era and cottages max at 7 in renaissance, but warehouses can go to level 2).
Format is: Structure population per level (pop with 25%)
village 20 (25)
towncenter 100 (125)
storehouse 20 (25)
warehouse 200 (250)
capitol 500 (625)
cottage 25 (31.25)
plaza 5 (6.25)
market 50 (62.5)
barracks 2 (2.5)
recruiting office 20 (25)
training yard 2 (2.5)
blacksmith 1 (1.25)
farm, fish, wood, iron, quarry 5 (6.25)
The following give 0:
library, university, parade ground, stone mason, saw mill, foundry, tax office, trading post (probably customs house), armory, lookout post, stable.
Note2: I used a spread sheet and the numbers are close don’t quite add up so help me out.