Walkthrough: Mario will arrive in Wooded Kingdom in Steam Gardens, quickly noticing the Denizens of the region that are quite upset. After landing, you can obtain some Purple Coins by heading to the ledge behind you. However, make sure not to drop to the forest below. Whether or not you obtain those Coins just yet, head down the main path. As you do, grab the Purple Coins hidden behind the large trees, as well as the regular coins under some trees and atop others.
At the end of the path, you will come to a Sphinx that asks you what you think Bowser wants from this specific kingdom. Cappy told you the answer as you arrived in Steam Gardens, telling of Bowser wanting the special flowers grown here. Answer the Sphinx's riddle correctly, and he'll move aside for you to continue down the path. As you head to a large area will purple puddles of goop, don't forget to nab the Purple Coins on the left. The purple substance, found in earlier Kingdoms, is painful to touch, but Cappy has the power to clean up these smaller puddles with his circular spin. From there, continue forward as you begin to head right toward Iron Road, and on your way, don't forget to obtain the Purple Coins you come to.