The size of your band depends on the allowed amount of Gold given (determined by which Deathmatch Level or Scenario you choose to play).
The middle/standard sized games are Regional Deathmatches which allow you to make your warband and an average size. Warbands in a game like this usually consist of about 4-6 Avatars depending on what supporters and training you give your Avatars.
But you can also play larger games as well as smaller games.
PS - I also slightly edited your title simply because the previous looked as though it was a general discussion thread (of which there is already one of) and the new title just makes it easier for people to realize what the thread is questioning
