For me it doesn't matter. The younger the better but if you don't have much tokens you can by good 5* older players.. My midfield has 5 29 year old players that were 5* but they grew to 6* naturally.
TuaMa: Season 3 team
Season 1: Cup Preliminaries and League winners
Season 2:Cup preliminaries, League winners and Champions League winners!
Season 3: League winners, CL winners Season 4: In progress.