You can find hotels for around 70 euros a night. But the best deal is hostels. For around 15 euro a night (dorm room), you can stay in places that could easily get 200 euros or more if it were a hotel.
Dinner is usually 20-30 euros, with a glass or 2 of wine. There is no tipping in Italy (you can leave a few euros if the service was excellent), so that is your total price. Lunch can be had at many of the open markets for around 5 euro. Breakfast is usually included with the hotel.