>>538009136
It depends on your opponent's deck.
Against loot sword the imperative is to avoid dying to an early Zirconia, so you keep Witch's New Brew, Melvie and/or Penelope, Sagelight Teachings, Edelweiss (if you run her) and Stormy Blast.
Against spellboost rune the gameplan is different depending on whether you're going first or second. If you're first, you want to focus on getting your DClimb to 0 cost as soon as possible so you hard mulligan for that first and foremost. You can also keep Witch's New Brew, Insight and Homework Time. If you have DClimb in your starting hand then you mulligan for your 5 drops since you need those to build your spellboost counter. If you're going second you're at a natural disadvantage since your opponent will be able to DClimb at 10 mana first, so you want to be aggressive. You still mulligan for DClimb but after that you want a two drop, Anne&Grea specifically (you don't evolve Bergent going second if your opponent is spellboosting a lot), and Norman to try and be aggressive with a double golem play. Save a Kuon and at least one Demonic Shikigami for your turn 9 so you can use your extra PP to make a Noble Shikigami with at least 14 (15 if your opponent has the Bergent crest) defense to save yourself from Satan->DClimb->Astaroth.
Against Crest Haven games end up being really grindy so you mulligan for DClimb and Satan, once you have those you fish for 5 drops and healing (Sagelight Teachings and Norman).
If you face any other deck, you should be fine with a standard mulligan for DClimb, Witch's New Brew, a 2 drop, and a 5 drop.