Yes, you can purchase a Setapp gift card in the "Gift cards" section of your online user account. Just choose an appropriate subscription option (1 to 24 months) and confirm the purchase. That's it! You have a gift card code that unlocks access to 100+ useful Mac apps.
Now, just share the code with your friend the way you prefer and don't forget to mention it can be activated in Setapp's user account. In other words, your friend needs to register with Setapp to use the gift card.
Please note that the current gift card functionality is basic, and we are going to improve it in the near feature to make it easier to share and use.