Decided to do the mini challenge to get my brain juices flowing.
Sometimes giving things to people carries a lot of meaning. Think the horse head in The Godfather, the "donations" politicians receive from people who expect favors in return, and the practice of giving away daughters to solidify political relationships between rulers. In what ways is "gift" giving more than it seems in your world? Is there are type of giving that is culturally standard? Are there particular moments of gift giving that were unique for what those gifts represented?
In the American Empire Under, gift giving is a common practice. Small items such as cloth, plastic, and stone jewelry and decorations are often given to friends and family at the whim of the giver, and hostess gifts typically include a little bag of mushrooms or Under insects. Anything small and cheap is considered a customary gift among most races. Somewhat larger gifts, sometimes of more expensive food or drink, or trinkets made of valuable materials, are exchanged by many during holidays, though it is very rare for the forced Yule holiday to include any gift giving. The amount of gifts that is considered proper varies among the races, with the fey tending to have access to more and thus having more to give, and the lycans giving far less due to exclusions from Surface contact.
The most significant gift an Under citizen can give or receive is a potted plant, the rarer and more beautiful the better. It is typically expected among all races that romantic partners proposing marriage would gift one another with some kind of living plant, however small, and if such tradition is not upheld, it is considered a slight against the would-be in-laws. It would be even more offensive to give a dead plant, whether beautiful or not, and a whole bouquet of flowers would be the social equivalent of a slap to the face and a spit in the eye of the recipient.
In the Russo-Asian Empire Under, gift giving is also a sign of respect and is considered necessary to cement the relationships between friends and family. The wide variety of races that inhabit the Under have made a much larger range of gifts acceptable, ranging from the mushrooms and cloth jewelry common of the American Under to blind fish-beasts, sunstone gravel, and paper trinkets. Surface-purchased food is a less common gift, as the Russo-Asian Empire has less to sell. The races within this Under also uphold the tradition of giving living plants as marriage gifts, though this has begun to slowly fade as the faltering structure of the Surface empire affects what can be bought and sold.
There are no documented gift traditions within the European Colonies and Pacific Empire Unders, as most of the populations there were annihilated after their various failed rebellions. The Atlantis Under and the Yellowstone Vaults, and whatever refugee population they may or may not contain, are simply rumor at this point. As there are no true ruling families in any of the Unders, political gifts are almost unheard of, and what little gang presence there is tends to be focused more on petty theft and rebellious vandalism while keeping themselves hidden from the human police and military forces. Some of the richer citizens of the Unders might attempt to bribe powerful Surface humans, but as this almost always fails due to the difference in value between Under and Surface money, it is something done only in emergencies.