Alright... now to do this properly, you have to have a lot of gold entering your city all of the time.
Farming NPCs is becoming harder as competition grows more Ballistas.
Making cities that exclusively produce Iron and Lumber is a sure-fire way to maximize your gold income. These 2 resources will always be in demand, and fetch for a high price on the market.
Unfortunately, iron also the highest idle population hogger in the game, meaning you need more cottages to make exclusively iron than you would a mix of all the resources in a city.
Here is how you can capitalize having that extra Population Capacity, and put to use a very little bit of the gold you earn by selling excess resources for food or stone.
Set your taxes to 3% in all of your cities. Anything more than 3% will require you to waste a spot in your city for another cottage instead of a Barrack. This will make your gold per hour go red. No big deal, you make millions of gold worth of lumber and iron per hour now. Always have a minimum 1 million gold in each city, either move gold around or sell excess resources to stay above the minimum. If you drop to 0 gold while your away, your heroes will begin to abandon you.
Now, Pray. That's right, get down on your knees and pray, in every city you have.
Prayer gives gold to your people in exchange for loyalty, and your loyalty will go to 100.
The gold you give is based on your population cap, and the prestige you get is based on the gold you give.
The level of your TH, your rank or title in the games promotion system does NOT affect the amount of prestige you gain.
After 15 minutes, it will be at 97, which is where it will stay because your taxes are set at 3%, you will be able to pray again.
Use your Loyalty as a Prestige Timer. Every time you see your cities Loyalty is at 97, pray again, in all of them.
25k gold is nothing and will gain you around 200 prestige in each city every 15 minutes.
Now let's do some math.
200 prestige x4 per hour (every 15 minutes) = 800 prestige per hour
800 prestige x3 cities = 2,400 prestige per hour
2,400 prestige over 5 hours of playtime in a day = 12,000 prestige
That's 8,400 Prestige in a week or 336,000 prestige in a month.
This is all on top of the prestige you get anyway from research, upgrades and troop/fortification building.
Once you are swimming in gold, you should do this.
Prestige is not only the 1st deterrent against an attack, it also elevates our alliance in the global leader board.