2 more points worth mentioning:
zeogold: How does gifting work?   1) The price of a gift will always be equal to the game's US base price or higher. Thus, if you attempt to gift a game that has a lower-than-base price in your region, its price will be increased to the base one.
zeogold: - While the suggested method of inserting a friend's email is an easy method, you can still give a gift without knowing the recipient's email address. 
 - Enter your own email and you will be sent a code which can be redeemed 
here. This code can be given to whomever you desire. People on the forum often use this method for giveaways (see: "How do giveaways work?") and trading (see: "How can I trade on GOG?''). 
  2) All your gift codes are also accessible from your 
order history, which can be useful if you accidentally deleted the e-mail with the code or you never received a mail in the first place (or if you can't be bothered to check your e-mail).