MarkoH01: I am no newcomer but I remember coming into this forum and mentioning a game which was then gifted to me. I did not understand why anybody should give me something without payment or sth. to trade for it. After I started giving myself I finally understood.
The first time I gave away a game to a stranger was in December of 2013. I had recently found the forums - I joined GOG in June, but didn't stumble in here until much later - and honestly I thought the gifting thing was some sort of weird commodity speculation. I watched for a while and tried to figure out what was really going on, but I couldn't break the code. Then it eventually dawned on me that these crazy folks were just giving games away to strangers.
I wanted to try out this weird custom, so when a game I liked came on sale - Robin Hood, a perennial favorite - I looked in the Gifting thread, or maybe it was the release NEWS thread, found a likely candidate, and PM'd the code. It was a total rush. I just looked up the transaction, and it was a gift to Niggles, who is still active these parts (though he or she ran under a different handle at the time).
Finances keep me from being as generous as often as I'd like, but giving really actually is its own reward.