In Ladida Plains 1-3 and if you have enough power in your vibe gauge go where the bridge is and use the joy vibe to fly up and find coins floating above donuts.

Go to the beach stage two. Slide down the hill and jump when you see the second starfish. You will find a lot of koopas. You need the ability that lets you get coins for defeating enemies. Kill them all then they will keep reapearing. Now I got about 20000 gold.