Giovinco will be just fine on the left wing. He's played there most of the time for Empoli, that I've seen. In fact, the times where he has been trequartista has been usually for the Azzurrini and even then he tends to drfit leftwards. To get the best out of his creativity and passing ability which is top notch, a central position is required. On the left, however, he taks on players, crosses the balls and cuts inside. Either role is fine with me.
Not in terms of playing style or roles, but on the left wing, positionally he can be used like Ronaldinho at Barca or Zidane at Real. That is how I would expect Ranieri to use him anyhow, with a midfield of Zanetti/ Poulsen, Sissoko and Camoranesi. Camo would be postioned somewhere between RM and CM (like with Lippi's Azzurri), where he can take advantage of his creativity, work rate, ability to hold the ball well and his wing play.
---Giovinco
------------------------Camoranesi---
------Sissoko------Zanetti
It's like a narrow 4-4-2. I know Sissoko usually plays on the right side of CM, while Zanetti is on the left, but with Gio playing rather than Nedved, Sissoko's running may be more needed behing Gio, while Zanetti sits in front of defence and Camo next to him.