Q: How long does it take for purchase to be taken from iTunes gift card

Hi Confused from sussex,

Your balance of credit through the iTunes store should reflect purchases very quickly. See this article for reference -

How iTunes Store purchases are billed

Specifically -

When you make a purchase in the iTunes Store, Mac App Store, App Store, or iBooks Store your account will be billed at the time of or shortly after your transaction

Thanks for using Apple Support Communities.

Best,

Brett L