Akatsuki: 6 people
Kage: Mizukage, Tsujikage
Sannin: 3 people
Sound nin: 1 - 5 people + Leader
Jinchuuriki: 4 people - 1 tail to 4 tail
Genin: Unlimited
Chuunin: Unlimited
Jounin: 1 - 10 people
Special Jounin 1 - 3 people
Med Nin: 1 - 10 people
ANBU: 1 - 10 people + Leader