You cannot use an existing Apple Account balance to buy or send new gift cards.
Depending on which card you have, you can convert its value into usable credit for apps and music: buy itunes card with apple store gift card
All gift cards must be redeemed in the same country or region where they were purchased. How to Use Your Funds You cannot use an existing Apple Account balance
Generally, Apple policy prevents using a gift card to buy another gift card. buy itunes card with apple store gift card