You can insert the Ko! Custom Gift Certificate plugin into any components, articles or modules, the only requirement is the content need to process plugin.
Here you see all the card available with all the card amount available (set in the admin)
Bellow I use Mosets Tree to display specific card with specific price.
Also the component is set to use the Paypal Sandbox, if you have a sandbox account you can test all the purchase process.
Remember this is all fake stuff, it is just for the demo of my apps.