sadly it is budget and I do really agree with your addition of Collective Brutality
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or Aqueous form
with this deck you want to swing in at turn 2, pyromancer cannot hit until turn 3 in this deck. I personally was about to recommend Monastery Mentor for all the prowess tokens.
I was able to take this to second place at a local modern tournament. A very interactive deck that was fun to play. I am working on getting a couple Thoughtseize to add to the deck.
You will need some form of removal to help clear the way for you to swing in for damage or deal with hard to address threats; I would consider Path to Exile, Murderous Cut, or even Vapor snag.