Five symbol stones are randomly throughout a level each day. If find all five of them you will earn a 500 coin bonus. You can find a set of symbol stones once per day, and if done consecutively, the coin bonus will increase.
When you encounter a large shiny question mark, jump into it. You will be sent to a bonus room and end up on a golden railway. As your speed increases, collect the coins and lucky eggs. Lucky eggs give you a chance to get mythical objects that help unlock more characters.
Daily bonus
Tap the daily sign in button at the main menu to collect a free prize. You must log in every day in order to make it to the end of the board. With each log in, you will receive more coins each consecutive day. Some days also feature a chest containing random prizes.
Meters
Above the "Sign In" button is a "Journey" button. As you play, you will accumulate meters which are automatically added to your journey progress. The farther you progress in the main game, the further you will get in your journey. There are checkpoints at certain distances which feature a chest.
In racing mode, instead of collecting coins you will get green magatamas. When they are collected, the bar at the top left of the screen will fill. After it is full, your speed will be increased temporarily. Although you will not earn coins in this mode, it does add meters to your journey.