Thanks to every one that replied,

Last season I bought a 23 years old scout, ending in 9, so very close to 7 stars.

In the season , he got 7 stars, but that's pretty much it, he didn't get better as I though he would.
What I can tell you is that I didn't train him a lot, he just played 2 games per day. So If I wanna buy more than a scout like skidz said I think, how do I make sure that he's going to upgrade a lot, and again, whit my small 100-125 tokens per season ?