It depends on what position you are training them as and how much you train secondaries vs primaries. Generally a "star" caliber player doesn't meet the need of many people for a good trainee, but keep in mind that all leagues are different as well as countries. The best thing to do is to search the TL and your Italian leagues to see where potential players are at skillwise and salarywise.
Another quick question, does potential have sub-levels like skills do?
The answer that some people will tell you is, no. This is because there is no absolute proof to show this technically however there are very strong indications that it does, so my answer (along with many many other people) is that potential definitely has sublevels.
Murray/Harris/MPJ/Grant/Jokic - 2020 NBA Champs