1) "Immediately put this card on top of your deck"
"Poker Winnings" - $5
Treasure
+$1
When you play this, discard the top card of your deck. If it's a treasure card, +$1. Then put this card on top of your deck.
This one is difficult. It basically has to be a non-action unless you want to work really hard to prevent crazy looping shenanigans. This reads as not very powerful, but putting itself back on your deck every time you play it gets way better the better the card is. Big Money buys Silver with 5 sometimes, and this will usually be a silver that puts itself on your deck for next turn, which seems really strong in that light. I thought about costing it at $6 or $7 and making the bonus be +$2, but I'm not sure exactly how good that would be compared to Gold. It's hard to judge without actually playing it.
2) "+1 buy. If you have any unused buys, put this card on top of your deck."
"Walled Woodcutter" - $4
Action
+$2
+ 1 Buy
At the start of Clean-up, if you bought one or fewer cards this turn, you may put this on top of your deck.
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The other two just seem annoying to implement in face-to-face play. Every player has to reveal their hand every turn, even if no one bought these cards, just because they're in the Kingdom? ._.