Q: I am trying to buy 2 songs and I click on purchase i already have 50$ redeemed in my account but its not using that money its suggesting my debit card. How can i get my gift card to be used then?

Hello there, AniChirglyan.

The following Knowledge Base article talks a little about the purchasing order of items through the iTunes Store.

iTunes Store: How iTunes Store purchases are billed

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

iTunes may still ask you for information from your card on file if that information has lapsed or needs updating. The card information on file has to be correct, no matter what purchasing option you will be exercising for this purchase.

Thanks for reaching out to Apple Support Communities.

Cheers,

Pedro D.