The hack here is obvious. 1) Purchase a 50 dollar gift certificate and get a 10 dollar gift certificate for free

2) Use the 50 dollar gift certificate from above and get another 10 dollar gift certificate.

3) Keep doing this over and over.

Here is what happens after each step:

1) Money spent: 50 bucks, gift cert $ 60 bucks

2) Money spent: 50 bucks, gift cert $ 70 bucks

3) Money spent: 50 bucks, gift cert $ 80 bucks

...and so on until you are satisfied.