You receive score for completing levels. This score is added to your current task and once the task is filled completely it is done. Each task will have their own score, such as gems for story tasks, minerals for mining and tracks for traveling. 
If your score wasn't enough to complete the task, you can boost your score with 50% bonus score!
You can add the 50% bonus by choosing one of the following options:
  1. Watch the Bonus Video
  2. Use 5 Diamonds
  3. Always get 50% automatically with your Golden Ticket subscription

You can also choose to skip the bonus. 

💡 Tip: A higher score earned in the level means a higher bonus score you can get through the ad or using your diamonds.
💡 Tip2: The Golden Ticket subscription has many benefits: no forced ads, always 50% bonus score, extra daily free chest and more!