OK, so you have noticed most towns in your magnificent empire produce exactly 1 shield and 1 trade because of waste and corruption, and you think you have a problem? Think again! If you manage these seemingly useless towns correctly, you will see you cannot have enough of them.
First rule: Do not invest! Do not waste a single gold coin on improvements or defense. Those towns do not need any public buildings, and if they are not your only home of a strategic resource, they do not need to be defended. They exist for one, and only one, purpose: To pay taxes!
First thing, make them produce a worker. Even with one shield, this will take them only 10 turns. Let the worker build irrigations. Forget about mines, roads and railroads, but build lots of irrigations. Food is never wasted, so your town will grow. Let it grow to size 7, if it has a river or lake adjacent, otherwise 6 will do.
As soon as optimum size is achieved, appoint as many tax collectors as possible without starvation resulting, usually 2 or 3. Put production on Wealth. This will result in:
1 shield converted to Wealth = 1 gold.
2 or 3 tax collectors collecting = 2 or 3 gold.
1 trade = 1 gold.
Which all adds up to: 4 or 5 gold without investment. Even better, if you have a stable government such as Monarchy or Communism, your size 6 town will support 2 free units, while a size 7 city will even support 4. This is why I advocate growing to size 7, where possible without an aquaeduct. 2 or 4 free units equal another 2 or 4 gold without any prior investment -a better deal you get nowhere.
Whiners may complain about waste and corruption. But I love those quiet places in the countryside, where nothing ever happens, except for gold coins being paid into my treasury. They pay for my rent, and keep my empire afloat.