You can gift keys to whoever you like.
At present it is best to purchase the keys in your own name and have them delivered to your normal email address.
You can then login to your BundleStars.com account to view the keys from where you can copy and paste them into an email, document or anything else to then send on to whoever you want to gift the keys to.
Take care to check if you're gifting a region restricted game. If a game is restricted to a region you will receive a copy appropriate to the region you're connecting from - check that whoever you are sending the key to is in a region for which the key you received is also appropriate.