Mulligans
General Mulligans
Dun baldur bunker lets you thin your deck allowing you to get to the beasts it also provides you with valuable stalling tools Vs aggro and combo decks. Vann the man (or dwarf even) provides a discount for all your minions. Tracking gives basically gives you 2 extra chances to Mulligan compared to just swapping it out as you do not use your first turn. mana usually. Harpoon gun gives you decent removal and possibly a discounted big beast or other useful card.
Going second if you have dun balder bunker I'd recommended coining into turn one to get those secrets out quicker. Vs demon Hunter you might wanna keep explosive trap as well.
A mid range tempo deck using secrets to start and the newly improved pet tamer for mid game tempo with vann for some super discounts.