I was going to put this in Easy Puzzles, but then I suspect they're not actually that easy.
1. The effects "+1 Card", "+$1", "discard a card", "trash a card from your hand", "gain a Curse" are in the set. The effects "+1 Buy", "+1 Action", "take a coin token", "gain a Curse" are not in the set. What is a rule that describes the set?
2. The effects "+1 Action", "+1 Buy", "+$1" are in the set. The effect "+1 Card" is not in the set. What is a rule that describes the set?
3. The cards Border Village, Grand Market, Ironworks, Goons, Stables are in the set. The cards Young Witch, Envoy, Merchant Guild, Oracle are not in the set. What is a rule that describes the set?
(The third one in particular is quite tricky, so in the style of Zendo, I will allow people to ask whether a particular card is in the set or not.)