I thought initially that buying good youngsters would be a smart choice because i would be able to keep training them every season and not have to buy new players to compete the next year and so on.
I bought good 18-19 yo for a lot of cash and trained them well.
but every new season, i see that the players on the TL are much better than my youngsters bought in the year before....and it seems i just wasted tokens and in-game cash to buy those youngsters because now i have to buy new players in order to compete at the highest level in the CL and the League. My old top players are not good enough to win titles anymore after just one season.
The smarter thing seems to be to always buy old players for cheaper price, players that have already been developed. The next season you sell these old players and buy new oldies that are much better. That way I waste less cash too and i am more competitive!