Hi, my civmates just told me about this post...I'm the person in the screenshot
I can share some tips and tricks that worked quite well for me, and I have never purchased a single civbuck. (don't know why you think I did)
1. I make most of my money in the marketplace, so civworld is basically a stock market game for me. I only produce the resource that I think is the most efficient for me to produce and sell/use.
2. I keep a "reasonable price" in my mind for each resources all the time, including commodities, troop, and great people. I buy when they are underpriced, sell when they are overpriced. This price changes with time, and how many battles are going on, but it's quite easy to get a true feel of how much gold a resource worth.
3. I also do some arbitrage on units during wartime. When the price of the units gets too high, I just buy cheaper production, build the units when it's cheaper to build them with production.
4. Buy units when the tech is just discovered, the starting price is very cheap.
5. I usually deposit my gold in commodities when the price is reasonable instead of just keeping them as gold. If you avoid overpriced commodities, be patient, you can almost always sell them double the cost.
6. Buy great people when they are cheap, most of the time it's more efficient to buy a great instead of creating them yourselves. Just do the math: using your reasonable culture price * the amount of culture needed for your next great. I only build them when culture price is way down, like below 60.
7. If you're playing to win as a person, not as a civ, there's some tricks that you can try. The king gets quite a few fame points more than prince and dukes, so planning "combos", that can first get you to be king, and then win an era or even two can be huge. It's possible if you have much resources on hand.
8. As a player that rely heavily on the market, he needs illogical moves from other players to make money. So basically I just make money from other players' lack of understanding of the game and impatience to get certain resource with higher price. Sometimes this isn't enough, the market price is just reasonable all the time.
This is the reason that I start wars all the time, this brings a lot of fluctuation to the market, and being the person that knows war about to start, I always keep a stack of production to sell at high prices (often > 1000). This is the time to reap big profits from production, and buy really really cheap food/culture/science/commodity because players mass selling other resources to get production. The wartime is just a great time for market oriented players. Even talking on global channel threatening an attack can up the production price.
I suppose the more players that play this way, the less efficient it will be. But this has worked really well for me, just some thoughts to share with readers of this post!