I managed to secure 2 wins by using 'Consume' to burn Chests to draw 9 cards every turn. However, the game balance feels overly dependent on RNG. The final stage require at least +3 Buys (of course with enough money). If the shop doesn't offer any +1 Buy cards or enough Buy potions, that run is impossible to clear. (Unless you can find your 'single' Errand Boy every turn...) This 'Buy-softlock' happens much more often than it should.
Regarding Haggle... As I recall, that was a 5-gold, 1-mana card, right? I don't think this card is functioning as intended in this time-limited format. Since playing it costs 1 Mana, it is strictly worse than a Coin if played alone. The scaling is just too slow: you need at least +1 Buy just to reach Stack efficiency and +2 Buys to catch up to a Purse. By the time you can consistently pull off +2 or more Buys to make Haggle really worth it, your deck must be already strong enough to win with basic economy cards. There is no real incentive to pick Haggle over simpler, more reliable options.
Yeah. I added a +1 gold to it to make it equivalent to a stack, but it's still not great until the end-game. Maybe I should just give it a + buy instead. I was worried that'd make it too strong (it means you can make a deck whose only job is to play 5 or 6 haggles plus some gold), but that might not be terrible. I'm also thinking about adding a card limit (like, the shop "runs out" of a card after maybe 5 copies), so that would let me focus the cards more on the case where you just have a few of them.
I see what you mean. I've tried to keep + buy clumsy/rare b/c I wanted to enable some of the more creative forms of payload (using Reconsider or Deconstruct, for instance, or the Haggle thing), but those are harder to set up, so the difficulty does end up pretty RNG-dependent. I don't want every run to just be "get a bunch of gold and +buy", though. I'll think about what I can do.
Somebody else suggested preventing duplicates in the prep stage, which I'm going to add, so that should make finding different cards easier.