Here are some suppliments:
It's actually like this:
beginner--watcher
then you choose:
trainer--circus trainer--circus master
tamer--game keeper--game master
tamer has the heighest atk in this class, and can turn monsters against monsters at the moment. Also, tamer can mob,
Trainer can train monsters to higher lvl than tamers do.
And you can't capture bosses, after all, boss monsters are their own boss.