it depends on when you're going and for what match. for example, for juve-inter, I got through 45 minutes after PREMIUM tickets went on sale, and already some allocations were exhausted. two/three days later, it was completely sold out, and I don't think they even managed to go on general sale as scheduled.
so I'd recommend you to purchase your tickets as early as possible but depending on the match you're buying for if you can't,it is pretty risky. I think in Turin you purchase at the stadium (maybe gate B) in person, I think I saw someone do that for the Juve-Napoli game. Of course there are listicket outlets, but I didn't see one in turin or maybe may have missed it/didn't find out where it was.