Yesterday's battle got me thinking whether it's possible to play DW without paying and my conclusion is that it would be so excruciatingly boring that it's not worth it. Imagine having to wait 2 days to get a 200+ drugs upgrade! Maybe it was possible at the start but i think a minimum of 15-20 steem is needed.
If you check back every 2-3 days, you will lose interest in the game fast. Designing the economy of a game isn't easy and there are a lot of unintended consequences. At least they get patched up fast.