We will be staying at a rental in Florence for 3 nights with a kitchen and would like to know about how much we will spend on groceries at a local market. Trying to keep an estimated budget and also make sure I have enough euro cash on hand.
You'll definitely save a lot on food if you use the kitchen and make your own meals as opposed to eating out every single one of them. Although I do suggest eating out at a local trattoria at least once or twice while you are here so that you can taste local Florentine and Tuscan dishes!!
How much you'll spend on groceries will also depend if your apartment owners have some of the basic staples on hand for you to use: sugar, salt, spices, olive oil.... stuff that you might use in reduced quantities but don't want to buy a lot of. At the market these cost less the bigger the package so maybe you want to find out if your apartment will have some basic staples on hand and if not, consider bringing a few things with you?
For 3 days, buy what you want to have for breakfast and you've already saved going out for coffee/tea + croissants/cookies/cereal/fruits/yogurt. If you do like bakery goods for breakfast, do buy those at a local "fornaio (bakery)" to get a wonderful fresh treat to start your day (the ones at the supermarket are not the greatest). All depends on what you eat and which meals you want to have at the apartment. You can plan to eat out at lunch and it in at dinner or vice versa. Consider what kinds of meals you want to make and only buy what you need. For the whole 3 days, you might spend less than 50 euros overall as long as you don't buy expensive meat cuts/fish/speciality ingredients.
Wine at the markets can cost as low as 3 euro-15 euro for really good Tuscan wines, including Chianti Classico. So if you want wines, add that to the estimate I made above.
In the center, go to the San Lorenzo market for produce and fruits! If you're in the Santa Croce area, head to the San Ambrogio market.
Olive oil and other staples might cost less at a small supermarket rather than there (try the Conad margherita at the SMN train station or the Billa on Via Pietrapiana or small Coop stores.