My tip: Go around and find the people who produce "odd" items. Toothpaste, pullovers, etc. Then start selling them the items they need.
The hard part comes when one of those companies go offline for a number of days as it is hard to find new buyers. (I produce wool and my normal buyer up and left with no warning. Now I took me two days to find a replacement.)
It might not make you the most money but it is much more fun.
