Beat the game on my 2nd go around. Here are some general tips that might help those having trouble:
1) Keep everything moving. Sitting on money or keeping ships docked is lost opportunity cost! (A good rule of thumb I found was to buy opium for anything less than 40 and sell for anything above 60). I wasn't really sitting idle for more than 5 seconds at any given time.
2) You can more or less see if the price of goods will continue dropping or taper off by how fast the price changes.
3) Limit risky business (unless you have the bribe card). Worst case is either you lose a boat+cargo or buy back for your own goods; both outcomes can really set you back.
4) Buying any good ~5 times in a row will cause the price to skyrocket; wait a bit between buys if the price isn't super low.
5) I usually buy tea whenever its under 30. Remember you have extra time to meet the quota in the form of Brits gradually getting impatient (resets every "year").
I hope this helps!
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