Three of a Kind is a Normal Trap Card.
Trap Cards are normally Set first and can be activated on a later turn, often in response to an action.
On the current TCG and OCG Forbidden & Limited lists tracked here, Three of a Kind is Unlimited.
YGOPRODeck lists Three of a Kind for these formats: Duel Links, Common Charity, TCG, OCG, Master Duel.
A listed print of Three of a Kind appears in Cyber Dragon Revolution Structure Deck (SDCR-EN031) at Common rarity.
Among markets shown on this page, the lowest listed snapshot for Three of a Kind is about $0.10 on TCGPlayer (prices change frequently).
