I think 4 players provide a good dynamic. The location of the covenant puts a limit on how many magi can live there, with 4 being the maximum as well.
I'll let Flavius introduce himself further. Once that is done, we can start discussing a character concept here.
Flavius, make sure you read the House Rules and Cosmology of the saga. The Cast will also give you a quick look at the kind of characters that already have been created by the other.