Q: In app purchase?

Hey Kimmy,

Yes, the gift card balanced is used first before the card associated with the Apple ID.

iTunes Store: How iTunes Store purchases are billed

http://support.apple.com/kb/HT5582

Order of iTunes billing methods

When making purchases, content credits are used first, followed by Gift Certificate, iTunes Card, or Allowance Account credits; your credit card or PayPal account is then charged for any remaining balance.

Thanks for using Apple Support Communities.

Regards,

-Norm G.