I'm not a big fan of Gift cards but since they are a good idea I just create this one from an 8½ X 11 cardstock (you can do 4 from an 8½ X 11 cardstock) is a quick and inexpensive idea right? and you can embelish as much as you desire and more personal. You don't have to use those standard that they comes with in some stores!
How to: (see pictures for details)
First cut a 4 1/4 X 5 1/2 cardstock (the same size as a card front, cut half and then half again). On the 5 1/2 side score at 1" and 3 1/2. On the 4 1/4 side score at 2/3 each side (see picture for details). Cut the side that you don't need. Ad red line tape to close the sides and embelish as desire!