well, I 'm not familiar with those % of quality as I 'm following the old version.
It's too hard for me to understand.
My strategy is to buy 5* fast trainers (having about 8 in a season) and train (or from games) them to 6*, early 7* at the end of the season.
Keep them for 4 seasons unless doing some tanking .
Fill the team with simple 5* players (and selling them after the season to get others from the next lv) and sometimes buying a scout too.
Of course they must play good.