Originally Posted by Patrickthetiger

You're not able to combine gift cards (or use your gift cards to purchase a $200 gift card online). Per Southwest.com...

"Up to four Southwest gift cards can be applied toward one reservation. Our payment system limits the total form of payments, so if the balance of the itinerary is more than the amount of all four gift cards, you will only be able to use three of your gift cards so that the balance can be paid with another form of payment that will cover the balance of the reservation (i.e. credit card). "

The easiest thing to do would be to book your next RT fare as two one-way fares. You can use 3 gift cards + 1 credit card for the departing leg and your last gift card + 1 credit card for your return leg (or 2 GC+1 CC and 2 CG+1 CC, whichever works best for the total cost of the fare).