My tip is save a few k up and go to the store. Define each player by ratings, and go to the lowest price and the shortest time left filters. Bid on the highest rated players that match your team skill - I did buy 15 pro packs, which I think is neccessary - it got me 3 elite players and a football outsider Mason Crosby. You need good kickers, qb, hb, recievers and a basic defense. I then go for the safeties, cb and then linebackers. I find the d-line and o-line both need to be decent at least.

I've been grinding it for a month now, and I'm 7-1 on my 3rd season in all and I just got into rookie-1

I would insist first on grinding out the Solo challenges. Do the training camp ones. It might get boring after a while but it's the easiest way to make 33k.