You receive one loyalty token for every loot box or 100 gold you buy. 3 loyalty tokens come with each special offer or random offer. If you own 3 loyalty tokens or more, you don't have to watch ads in between games.
What are the "Special items"
At the moment, there are 6 different costume sets you can unlock with loyalty tokens:
Overview of tokens needed
The knight outfit used to be the first set of rewards, but got replaced by the dino outfit. It is no longer available but past owners of the skin kept it.