What i would advise is

-dont heal ur st, let him heal himself, or if too long let him be injured for a couple of days minimum (change formation or play amc at st or do what u gotta do)
-sell players, keep 15 or 16 players only, ull get only 3 or 4 injuries per season
-dont spend tokens on red packs, its like drugs when u start u need more and more always
-be strong