Q: I am trying to buy music with my $25 dollar gift card but its taking it from my debit card instead. Help?

First, are you positive that is what it is trying to do?  You don't describe the situation exactly.  iTunes may be requiring you enter credit card information for account use authorization but will still charge the gift card balance for the actual purchase.

For a few things such as purchasing gift cards, those can only be done with a credit card, not another gift card.

You must first Redeem your card to the iTunes account.

Any purchases will first be taken from the gift card account.

-> http://support.apple.com/kb/HT1574