I Never buy tokens.
The game is set up so it's impossible to 'build' a team long term, you have to replace players every season as they can never train fast enough to catch up with the star loss every 'year'.
Only way round that for me is to not get promoted every season. Tanking is quite a contentious issue on here but to me it's the only way to go if you like building a team to keep for a long time.
By tanking you get to build up reds and greens, and by watching a few vids you get a few extra tokens every year.
Usually when I get promoted I'm in a league with players a level higher than me as well, so my scouts are 7* instead of 6*. A couple of them every few years on top of trained up academy players and it's fun to build a good team.
I know it's not the way the developers want you to play, but it makes it more realistic for me as a 'manager', not many promotions, lots of young players, and a couple of stars arriving every few years. I hardly ever use the transfer market.
There are 5 'scouts in my team, 3 transfers and the rest came from the academy.