Mulligan:
Against Warrior search for Molten Giant and Sunfury Protector, they will overturn the result, also look for a Defile, in the first part of the game can be really useful
Against Mage look for Dirty Rat and the Cult Neophyte, Mage is completed stopped by those two cards, make sure to have a removal when you use the Dirty Rat
Against Hunter there isn’t a really good strategy for me, only just push more damage as you can and use at max of his power the Spice Bread Baker to not die on turn 5
Against Warlock take the control of the board whit the Goldshire Gnoll and a powerful Dark Alley Pact that evocate a 9/9 on the field.
Now is returning Shadow Priest, but I didn’t encountered it, so I can’t help you, sorry,maybe is something like Warrior and another powerful Spice Bread Baker