In the Urban Dictionary you can find out that the word Gig has many meanings around the world. In Thailand it sounds like “gick†or gik†but normally you write Gig. It means according to them
Some one who is more than a friend but less than a boyfriend. One who falls between the spectrum of friend and boyfriend/ girlfriend.
One can have more than one gig. One can also have a girlfriend and a gig at the same time.
Gig covers the fields of friends with benefits, booty call, and unofficial boyfriend/girlfriend.
But it is something sweeter then booty call because it is more friend and booty call is more a late night call when you are drunk and horny.
Do not confuse Gig with bar girls, prostitutes or similar things they have nothing to do with Gigs because a Gig is a friend and should never take your money. You can give presents and pay for dinner like normally friends do but not exchange services for money.
While I agree with most of what you say here, I don’t think it’s necessary to make absolute rules of what one can and can not do regarding Giks. One of the reason why gik fad became so popular among the masses is because it offered a ‘casual’ alternative to all the serious dynamics of relationships that were governed by so many rules of what one could and could not do.