21 22 44 19 6 12 ??
Is this a "one shot purchase for next game only" -- or a permanent addon to the deck that you may draw again in the futur sessions?Permanent (unless you later trash and replace that player, which is possible in long games)
Is there a moment where you must reshuffle your whole deck, to have this permanent process of amelioration ?Sure. Whenever you've run through the deck, like other deck builders. You're playing six or more cards per game and buying probably no more than two, so you're progressing through the deck even with stacking the new cards at the top of the draw stack.
By minigame 4, there's a good chance that you've triggered a shuffle and start seeing purchased cards show up in combinations.