..., but my economy always tanks, or jumps up and down in large spikes. ... The problem I think is my teamsters aren't taking to food to the docks and market fast enough for me to make a constant stream of money. ...
If you have no exports other than from farms, then the spikes are from a combination of the harvest cycles and the workers cycling through several needs modes - not just the teamster's work cycles.
Too many urban myths got into the repeated comments, and so a few facts have been overlooked.
The economy can work without any teamsters at all; the workers will carry their own goods but they are less efficient.
The Teamster's Office must be placed near to pickup points - not the delivery point. On random maps, the original one is never in a good location. But no matter how well placed they are, they can't carry goods which are not yet available.
Running too many teamsters is a fast track to making your economy tank. Add them only when you see the workers are carrying goods away from the production building.
warning is a real bug connected with the Ranch - the cows and goats are incorrectly counted as people. Check out your food statistics before you hit the panic button.