combining visa gift cards?

There is no way to combine them all that I know of. If some cards are by the same issuer, you may send an email to that issuer and ask them the question directly.

Just use both for your purchase. If you are shopping in person or online where they accept credit or gift cards, you can always use multiple methods of payment. You cannot combine them onto one card but you can use them at the same time for the same purchase. Buy yourself something nice and happy holidays!