Devil from Missoula- This is what I am doing more or less, also think its the best plan. Here is my team:

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The red guys are the 18 y/o's I picked up this season. I get 3 per season. I take them one by one and push to 8 stars, and play very few games with the before they get to 8. I use at least 95% of my Rests on these kids for the first three weeks of the season. I only use rests to heal players for Association games otherwise. And keep my team healed by playing my subs as much as possible, and I also don't hesitate to play tired players against bad league and cup opponents.

The green guys are 19 y/o now, and I picked them up last season. I will spend the rest of the season taking them each to 8 stars. Zinidizu is like 139%, and the other two are 131% and 132%. They have improved from around 121-122% at the start of the season to 131-132% now by just playing games and training without using rests (ie when they get to 99%, I run drills to keep them from hitting the roof). I will now use all rests I get to get them back to 8 stars.

The yellow guys are the ones I picked up 3 seasons ago. I have not used any rests on them at all basically this season. The GK, Christeoletti, is 125%, the DMC Manté is 121% and my DL Roberto Cesare is 128%.

The other 2 are Portugese 22 y/o AMC Niko Candeais and the French 22 y/o DC Liliam Salem.

Candeais is like a machine. I picked him up as a 3 star 18 y/o when I was short on cash, and he has just performed extremely well:
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I have not used any Rests on him, but he is still 124%. Next year he will be 105-106% and I will have to powertrain him I think. But he stays fairly on a high level thanks to all MoM.

Next season I will be looking for 2-3 of 18 y/o players in the following positions, DL, DC (a must, its not worth to waste further Rests on Salem and he is falling behind), DMC or GK.

Before the end of this season, I am selling the players underlined with blue. They are guys that played last season for me (the 5-6 stars), and the 3 star players are Free Agents I picked up this year that is retiring. Hence, I will have 12 good players of 14 for my cup draw, and one 4 star and one 2 star.

I still face very tough opponents, this is the guy I faced in the semi's for example:
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He was 131% then and I was 126%. Lvl 7 against lvl 5. I think its good to manipulate the system a little bit, because otherwise you run the risk of facing someone you don't even remotely have a shot against (160-180% teams). I am still a lvl 5 manager in a lvl 9 Cup. Lvl 10-11 gets darn tough to be honest.