I second this whole post; great advice!
I'm in the exact same boat as you; pre-ordered the game (Jackie Robinson edition, not digital deluxe) and have also spent no additional money on the game, and no crazy flipping either. Just by grinding the game and saving stubs, I was able to buy Trout about 2 weeks ago for 370,000.
I was lucky enough to pull Gerrit Cole and Cody Bellinger in packs so far; I sold Cole so that I could finish the NL West to get Steve Finley, and I also locked in Trout to finish the AL West.
I spent at least a few hundred dollars on the game last year buying stubs (mostly when they had the stub sales where you could get 150,000 stubs for half price a few times) but I'm happy to say that I am committed to going No Money Spent this year, as it makes the grind more rewarding. I did finish the Live Series Collection in MLB 20 around August (I think?) but this year I'm taking my time to finish the collection, as I like playing with a lot of the early season cards that I wouldn't normally use if I already had Ortiz, Soriano, Chipper, etc.