It's really all dependent on schemes and strategies. I've only recently begun playing, and I find the hardest part of the game is before it even starts. I would initially suggest looking at PullMyFinger for suggestions on when best to run each master, or Schemes and Stones if you're into podcasts.
However you want to experiment with models and when to run them to find your personal playstyle. The game has a big learning curve, so don't be afraid to make mistakes.
I will also suggest that you stick to 2 masters and work from there. There's already so many models to potentially run in each situation, that are not masters, that keeping the variability there down to a minimum is a good choice. That being said, I would run Jack Daw and the Viks, as they'll give you a good spread of capabilities between models, control and killiness respectively.