This is a disclaimer that this is easy but not quick.
Head into Thwomp Volcano. Go to the place with the spinning thing. (Sorry, not sure what it's called) The Thwomp will ask if you want to play for 100 coins. Say yes and go for normal difficulty. Collect as many gems as you can.
Coins: Keep on getting flowers to get 50 coins per spin. Maximum coin gain per game: 200 coins.
Beans: Keep on getting stars for 1 bean. Maximum bean gain per game: 6 beans but -100 coins.
You could get 2 flowers and 4 stars to get your money beack and get beans.
Check out commments to see the order of the symbols.