Disney's affiliate program doesn't offer commission on the sale of Disney gift cards, only on products from DisneyStore.
You may be able to luck up and find a Disney gift card on one of the unwanted gift card resellers like PlasticJungle, Cardpool, or GiftCards.com, but if they ever have any in stock they must get sold fast because I never see them there. If you do luck up and find them, you can earn cashback at QuickRewards.net on all three of these websites (around 1% for PJ and CP, and 3% at GC).