Can I sell gift vouchers?

Yes. Use Session Bundles. Click on Promotions at the top of your admin panel and then 'Create Promotion'.

Normally bundles are locked to the person who buys them to be used by themselves.

To make it a gift voucher that can be shared, toggle this option:

"Allow this bundle to be bought as a gift"

Now when someone buys the bundle they can share the code/email with someone else to use it.