Quest 7 of 8
Go Mining (6 times) - 12 gems to skip this task at 1 go.
Collect Birthday Treats x1 - You may be able to progress this task from buying from others but I'm not 100% sure. Try buying a birthday treat and see how it works for you.
Make a Pinata x1 - You will a total of 18 birthday treats to complete this and the next Goal.
My advise is that you dont gem your Mining task until you have purchased 18 birthday treats. You may also need to spend 14 gems for task 2 if buying doesnt count. Only gem through once you are very certain you have the ingredients and time to complete the rest of the tasks in Goal 7 and 8. Hope this helps.