Musacchio(DC) VIllarreal - can be got for around 1m in 2nd season, becomes unhappy every game on mine.
Joris Delle(GK) Metz - Turns very good, can be bought for 500k
Johan Cristaldo(ST) Velez - Always works well for me, for 3-4m
Raul(D/WBR) Paranaense - Is quality after 2 or three years, cost 5m
Philipp Prosinek(ST) Chelsea - Can be bought for 500k 2nd season, can be very good.
Lautaro Acosta(AMRC) Sevilla - Is always transfer listed half way through 1st season, for 2m tops.
Lacina Traore(ST) CFR Cluj - Becomes one of the best Target men on the game, cost around 2m
Ahmed Khalil(ST) Al-Ahli[UAE] - Can become quality, for 3m
Taufic Guarch(FW) Estudiantes Tecos - Becomes quality on some saves, for 5m.
I could keep going, but, I cant think of any at the moment