"Training schools" for deviants? Wut? How would you recruit enough people to make this worthwhile and how could you trust anyone enough to teach them to do bad things? If such a thing ever existed, it would be destroyed once it was discovered (and it will be discovered), making the whole concept pointless.
There is not and cannot be a "safe way" to practice being a deviant just so you can get good enough at it to best other players.
The way you get good/better is by doing it ... and surviving. Do it solo. Do it as part of a gang. But the doing is the way.
The way you don't get good at it is by getting caught ... and dying. This is probably why in the real world, deviancy is pretty limited relative to the total population. Most are incarcerated and/or killed.