My advice:
1.Dont buy expensive players coz at the end season all will drop 20% and just a waste of tokens to spend...
2.Buy 18y.o players wo sa which is pretty cheap. Maybe can get only 1 token as nobody wants him. Train as usual. Collect free green packs watching videos.
3.Collect the green packs and keep it until a week. When u accumulated 210 (30 * 7days) tokens then power train the youngest players u wish to upgrade and feel he has the potential to better.
4.100 tokens basically can power train 20% for a players for one shot. If u train an 80% level u can upgrade him easily into 120% which is decent. Repeat this for 4 weeks and u already have 4 players with 18y.o upgraded into 120% which will be 100% rater the next season.
5.Accumulate the tokens and dont spent unnecessarily that u will regret later. Just keep it piling up.
6. Dont obsessed with special abilities actually it doesnt give any advantage. Just a pure bs. I already done testing my none s.a players easily beat up oppenent with pretty much same qualities but with all s.a players. Sa actually a way design to waste your tokens and greenpacks (people buy gp just to upgrade s.a players with is absurd coz it does not give any advantage at all)
7. Never train players with s.a. just wasting your green packs. Better upgrade him into upper level. If u dedicated enough, u can maintain full squad with 7-8* level with just power train each. But it will takes time u must be patient. Maybe a few season later. But still better than wasting to buy in expensive scouts.
8. Once a while there will be offer 79 tokens to get free sponsored 20yo 119% players. If suit your tactical then go buy him as it is a better deals than scouts offering. Powertrain him into 140% just takes 100 green packs but it will spent better to upgrade him u will never regret.
So good luck. Dont waste unnecessarily your precious tokens.