Hey there!
How you need to go about filing taxes, and for what amounts, depends entirely on where you live. I do know that Tapastic requires US residents to sign a particular form, and non-US residents to sign another form (the non-US one is called W-8BEN), if you earn more than 600 USD/year.
As for the ad-revenue - you can only get it paid out to you once you reach a total amount of 25 USD. So if you've only made a dollar so far, you can't get it transferred to you at the moment; you'll have plenty of time to figure out the tax-issues before it's time to put that money in your pocket. : )