Apple gift cards
My apple gift card will not let me purchase anything
Where are you trying to use the card? Apple Gift cards aren't acceptable in the App Store/iTunes. Only App Store and iTunes Gift cards work.
If you have an App Store/iTunes Gift card, have you redeemed it to your account? Does the added amount show in your account balance? What happens when you try to purchase something?
If necessary, contact iTunes Support. Either use the form or scroll to the bottom of the page in the 2nd link. Follow through the screens to get a chat or telephone option. You may need to pick a problem that is slightly different than yours to get a chat option.