This article briefly covers how to remove gifts from a Giveaway or Social Giveaway campaign.
Removing gifts in a Giveaway campaign
Click on the Manage navigation item at the top of the campaign. Then click the checkbox of the code you want to remove and hit the Delete button up top.
Removing gifts in a multi-use Giveaway (social) campaign
In a social giveaway you'll want to go to the Settings navigation item at the top of the campaign. Then scroll to the bottom of the Settings page and hit Reduce gifts, this will will allow you to reduce your quantity of gifts for that campaign.