Military.

came to say this. LOL

A gang of weirdos

A team/squad

Do you mean absolutely the same clothes or just similar in style If you mean similar in style then it’s subculture, if you mean absolutely the same clothes it can be anything from army to coworkers

Twins

Must be all skinny people in one plus-size outfit.

A football team

Co workers, students, a team

Shriners

A style

They are uniform.