Various General Tips
Use Pause Blocks, in Mushroom Kingdom, to take a break and plan your moves. Use them to scan the area for enemy locations and path panning.
If you manage to hit multiple blocks at once you may end up getting double the rewards.
At the end of the stage prepare yourself to hop and grab the flag pole. Getting your hands on the top will be rewarded with an extra 10 coins and the best way to it is by activating Mario's mid-air Spin Jump.
To unlock and play as Toad you need to link your Nintendo account to the app. Once you link it to back to the main menu, hit the My Nintendo bubble and under the rewards tap on Toad and hit redeem. Then go back to the main menu and hit the gift box and select all.
To unlock princes Peach you'll have to successfully complete the entirety of World Tour, which consists of six worlds and 24 levels. Once you get to the end and rescue Peach from Bowser's clutches, she will become a playable character.
The rest of the unlockable characters - Luigi, Yoshi and Toadette - are unlocked by playing through Toad Rally, the app's other game mode.