I want to purchase Minecraft Realms for my friend as a gift. Is there a way I can do this? I've looked at the FAQ but it doesn't have anything about that.
You can try logging into your friend's account (with their permission) and using your credit card to buy a subscription on their account.
Other than that, it appears that it is not possible to buy a subscription to Minecraft Realms for another player. There are Minecraft Prepaid Cards but it is unclear whether they are to buy the full version of the game or if they can be used to add currency to your account.
Questions about Minecraft Prepaid Cards can be answered by customer service by filling out a question form here.