Generating new traffic is always a pain... do not use any bulk email campaigns, they usually only result in your sight getting taken down unless you host in China , Korea or other eastern country..
A direct mail (snail mail) might work for your type of offering? I like the idea of a one stop shop for gift cards myself..
Google adwords works wonders but can be pretty pricey depending on what type of site you are working.. .My hosting site takes $15 per click to reach the top 10 (yea that is 15 dollars per click).
You can put some test campaigns together to get an idea of costs for free...
You know what would be cool, is like Capitol One does, they allow you to create your own card face...