Dwellings are one of your main sources of gold income. The dwellings are your tax-farms and they provide a passive income yield just like farms produce food and lumbers wood.
You want to prioritise dwellings as you build up and progress through the building levels. Gold is a high demand and low supply ressource which you will need a metrix ton of to upgrade your dragon and boost your immortals.
lvl 45 = 522.5 gold per minute
My Dwellings produce 31,350 gold per hour at level 45, times 6 that is a solid 188,100 gold per hour or 4.5 million gold per day (with talent and 9/10 Gold Piles tech).
Because dwellings are so very important to your total gold wealth, you want to prioritise upgrading not only these buildings, but also the technology related to dwellings and gold production.
This talent is steightforward and insanely strong. Your dwellings produce a ton of gold for you as your citizens are taxed minute by minute. Read more about gold talents. This talent is a plain 10% boost to the production of your dwellings. You should always have this talent on.