Depends how many gelatos you want or how many bags you buy in Pisa. I went on a bus tour and stopped at Pisa. Lots of food places. Quite busy. A couple of Euros for a soft drink. Lots to see in Florence for no money. The market, Ponte vecchio, Piazza Michelangelo ( bus ticket 4.50 for a day ) but Florence is small enough to walk around. P M is on a hill tho. Need a bus unless you're really fit. FANTASTIC view of the city. Not to be missed.
Churches, some cost a few Euros. And you need to cover arms and legs in most churches. The Uffizi costs a bit. Can be booked on line.
Firenze has lots of statues in the street. Designer clothing stores. Lots of places to sit and hang out.
Food, 10-15 euros at a restaurant. (Or more, of course if you get wine, dessert) Cheaper at a cafe. There's a nice big rest. nr the Duomo, on the left as you stand in front of the Duomo. Don't miss the Duomo. Better outside than in. Stunning, in fact.
Reasonable prices at a supermarket. Pitti Palace, you pay for each part you see. If you want just the gardens, one price, gardens and one or two places inside, price increases. Can be dear. 8 euros up, prob. This was 3 yrs ago so prob more now.