Taxman in civ 3 produce only 1 gold, so it is much better to put your citizen on a roaded tile. If you got a marketplace, this will multiply your trade commerce but not taxeman. Also your units are supported by money not shield so maybe you have too much worker or military units.
To produce lots of gold its good to be a republic but built marketplace first then built cathedral to grow to city size 12 assumuming you have some luxuries to keep poeple happy. If your city riot then give them 10 luxuries. Adjust the taxe slider form 60-80 % research, search for theology, education and banking. A republican city size 12 with a bank,cathedral and university is top of the line. Be sure to have road on every worked tile.
