Ego Boost is a Quick-Play Spell Card.
Spell Cards are usually activated from the hand on your turn unless their type gives another timing window.
On the current TCG and OCG Forbidden & Limited lists tracked here, Ego Boost is Unlimited.
YGOPRODeck lists Ego Boost for these formats: Duel Links, Common Charity, TCG, OCG, Master Duel.
A listed print of Ego Boost appears in Battle Pack 2: War of the Giants (BP02-EN164) at Common rarity.
Among markets shown on this page, the lowest listed snapshot for Ego Boost is about $0.04 on Cardmarket (prices change frequently).
