The ShiftstonedEternal Power Calculator is a deck-building tool that visualizes your odds of drawing enough Influence and Power based specifically on the cards found in your deck.
I'd go -3 Mortar +3 Slope Sergeant or Jotun Punter. Jotun Punter can provide the last bit of damage to close out a game, and Slope Sergeant can draw more cards when needed and often comes out before turn 6. Meanwhile, Mortar doesn't really do much more than an expensive Torch.