Well, the Camarilla requires a Justicar, a Prince, Two Primogen, and Two Archons. So it requires at least six members. I would hope for at least 10 Members of the Camarilla. At least one memeber of each of the Clans in that group.
Then, the Sabbat requires at least two members, and that is so there is a Tzimisce and a Lasombra.
The indy clans I would want at least one member of each. Meaning there is another Five more players there.
And I would like to have at least five Clanless.
For a lower limit of players at 22 players. The more the better.