There are several jokers that add a card to your deck every round:
Marble Joker, uncommon, adds a Stone Card every round
Certificate, uncommon, adds a card with a random seal every round
DNA, rare, duplicates a card every round
Start on a deck with 52 cards (ie NOT abandoned), get one of these jokers early in the game, and use Standard Packs and Spectral Packs to gain cards and you should get it before ante 8.