Does a Gold Gear count for the Legion keyword?

No, playing a Gold gear token does not count toward the Legion keyword.

According to Rule 738.1.c, the Legion condition specifically checks if you have played a Main Deck card this turn. Because Gold is a Token, it is not considered a Main Deck card.

Relevant Rules & Rulings:

• Rule 738.1.c.1: "On spells and on play effects of permanents, [Legion] is functionally short for 'If you have played another Main Deck card before this one already this turn...'"
• Official FAQ: "Does playing a token (such as from activating Herald of the Arcane) count towards the Legion ability? Ruling: No, playing a token does not count towards Legion ability. 'Card' only counts Main Deck cards, and Runes and Tokens are not cards."

While a Gold token is a "Gear" and can trigger abilities that look for Gear (like Pit Crew or Ornn, Forge God), it fails the "Main Deck card" requirement for Legion.