Breakfast with coffee and a pastry in the sunshine in one of Florence's many squares, join the locals for lunch in the less pricey area of Florence, you can work up an appetite by wandering around the fresh produce, then dine on great-value pasta for just a few Euros: wash it down with a cold beer or glass of house wine.
You're in Italy, so ice-cream is a must.
For a good meal with the spirit of Tuscany, visit CNN Florence guide:
CNN Florence guide