Unlike most other games where you have drug dealers trading goods and low buy, high sell, and no time limit, this one is unique. It adds a certain twist that most games don't. I mean, who would think of a game where you trade tea instead of other things like drugs or weapons. Although I wished that the prices of tea would go down alot more, those damn british teamongers. Anyway, for any person that would like to know a good stradegy for it, here it is.
Always buy low but sell to ones that have like 20 chests for 85g a chest. That's a good deal. BUT, never ever buy too much at once. If there is a REALLY good deal for opium, buy about 2 or 3 30's. Otherwise you may wind up crashing the market and opium prices would skyrocket and never go down 40, just like i did.
Almost never go into a risky area because I found that they always bust you. And it sucks donkey dick. So try not to overload many docks with opium at once. You could find yourself with little docks to choose from.
Lastly, if you find yourself falling behind on the deadline, DONT PANIC! You could make a fatal mistake by buying a really bad deal. Check the prices of 15 and 5 as well, not just 30. Sometimes 15 could be a better deal than a large bulk of chests.
Hope this helps some of you! Excellent game btw. :3