Not foolish to play, 11B10. Just foolish to play anyone and everyone unless you can win >70% of the time. Before that point, you pick your matches. I've got a crappy 50-something 1v1 winrate, but I don't often lose coins, because I only play against people I'm at least 80% sure I can beat. 😉
Where did you get 70%? 5 coin small earth games I win 4 for winning lose 5 for losing. In order to break even I need to win 5/9, which is 55.5555555555...%. To make a profit I only need to win 56%.
As for people saying 20% is greedy, Fizzer hands out a lot of coins for free.
Oh my goodness. 11B10, as plenty of us have said, anyone can get free coins from the coinwheel on the app, or by entering raffles that appear every hour or so in the global chat.