Well it depends, are you willing to spend T/green boosters to get him to Q60 (7*) or not? If he is Q57, then he will need another 45SKP (doesn't need to be precise) to reach Q60 (75SKP). You will need like 50 greenies (differs as well) to accomplish it.
It's almost all about prioritization and Of course how much $/T you have in your owing. But when I buy scouts, I always by the ones that end with a 4 or 9 and are only 10 - 1SKP from 7*. This way, when I buy a 6* - I get a 7* instead and could use him for a xtra season.
