( WARNING : heavy gameplay spoilers )
for anyone interested, i'll kill the fun and summarise the dominant strategy.
1) buy ONLY an initial +20/30 score 2) always upgrade score until ~250 3) upgrade 2 cards with draw-time-exp 4) remove cards until down to 6
theoretically, this gets you down to a 16 day record. not 100% sure, hard to test.
there's a lot of dead-end strategies so i can't fully explain the rationale, but it basically comes down to "only 9 exp" being worthless
you need 10 in a single day, and 10 is a big number. especially when you're starting at 0 with +0. that takes a _lot_ of upgrades, and every upgrade costs a ton of money
you can farm passive income of course, but that's slooooooow. it's the easy inevitable solution, by farming up to 500 passive and upgrading a card to +10 exp. slow slow.
but it turns out that a simple infinite of {draw time exp} + {draw exp} is just enough to win, takes less upgrades, and those upgrades cost less money. nice.
and upgrading score instead of passive is more RNG-dependent, but still gets you to hundreds of gold much faster
so keep a small tight deck, upgrade as often as possible, and pray.
(i'm skipping some details, like removing down to 5 and then buying a Draw card to play your highest score card twice, but the general point stands. because regardless of theory, you'll often be wasting days without upgrading or progressing in any way. a perfect run is extremely unlikely. RNG giveth, and RNG taketh away.)