I think for maximum Leeroy it should be an event so that there is no planning whatsoever
LEEEEEEEEEEROY JEEEEEEENKINS
3$ Event
+1 Buy
+5 Cards
Gain a curse to the top of your deck.
If this is the first card/event you bought this turn, return to your Action phase.
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In games using this, when you trash a card, the player to your left may have you shuffle it into your deck.