Managed it once again, and this time I almost managed to achieve a loop of zero-cost cards that do damage or gain gold.
Need to remove a few more cards for that. If I can ever get “remove Exhaust from a card” with the card that removes one card from the deck and exhausts, that’ll be easy; otherwise it’ll take a few more removals at every opportunity. But I think if I can get a deck smaller than 10 cards (not counting cards that exhaust such as those that gain more energy, and not counting the cantrips themselves that are free and draw more cards), I can loop playing as many gold-gaining cards as I have until I have however much gold I want, and then play as many damage cards as I need to, to win each fight on the first turn.
Looking forward to pulling that off.