I think the best thing you can do in this game if you look at a lot of the teams that have had sustained success at the highest levels is be patient. If you know you're not gonna promote don't waste too much money on players. I wouldn't buy a ton of non-trainees if I knew 100% I wasn't a top 2 team in the league. That's how a lot of teams run out of money and kind of screw themselves over long-term. Do the bare minimum from a cost perspective of what you can to stay up in the league if you have a gameplan to get to NBBA. If not, no shame in relegating, getting your arena optimized, getting some bomb trainees, and restarting.
Money is really everything in this game in the long run.