If your visa gift card is the same as the ones I've used, then you need to charge only the exact amount (or less) on the card. For example, if the visa card has a balance of $50, and you are trying to pay for a $60 item, you need to pay the $10 in cash first (or another card if they let you), then use the visa gift card for the exact balance on the card.
For cards like these, I find it easier to buy gift cards with them so I know the exact amount. I've also bought Disney Dollars for the exact amount of the card.
Hope this helps!
