The Mercato Centrale upstairs food court is absolute bedlam. Quality is better than in the US (duh), but mediocre by Italian standards. I got separated from my husband, and even though I'm a 6 foot blonde who sticks out in a crowd, it took 20 minutes to find each other again. Getting a place to sit was a bloodsport.
GROM gelato. Go there, please. Ditto for Konnubio restaurant, lunch or dinner are brilliant.
Regarding any itinerary, but especially Florence:
Do less, but do it better. There is only so much world-class art you can absorb in a day.
Know where the attractions are relative to each other so you don't criss cross the city.
And know what days they are closed!
For any top museum or landmark, be the First Entry of the Day. Be half-finished before the tour buses arrive.
You can no more "do" the Uffizi than you can do the Louvre or The Met in a day. Plan which paintings you want to see, download a gallery map and mark their location, and then be strategic when you arrive.
Skip the line tickets are essential, and here's a reality check:
At the Uffizi in midApril 2019, the skip-the-line line was long before they opened for the day. Once we got up to the door, security inspection took at least 20 minutes, and then the line to go through the turnstile took another 20 minutes. Allow 15 minutes for a bathroom visit. Take only a modest purse; a backpack or large bag means that you will have to deal with the bag check line, too. Later in the day just gets worse.
At the Accademia with our skip-the-line tickets, we were almost the first in the door, so we got a good look at the David, but within 30 minutes the room was shoulder-to-shoulder. Pro-tip: You can save your time and sanity by seeing an excellent replica of David in the original location at the Piazza della Signoria, if that's all you want to see at the Accademia.
Same crowds at the Medici chapels but worse organization.
The line to enter the Duomo (skip the line tickets were not possible) snaked around the building by 8am for the 10am opening. The line never got any shorter in the 18 days we were there. Attending Mass is your best bet to go inside. By the way, the Duomo's art is mostly in the Duomo Museum, not the Duomo itself.
To see the Ponte Vecchio, we arrived right after breakfast to watch the shops being set up for the day. There were beautifully carved medieval doors, but within an hour, the bridge was too crowded to see anything at all.
In contrast, arriving at the Pitti Palace at 9am, tickets were half price for the early birds. In most galleries -- all filled with masterpieces! -- the only other person was a bored guard, looking at his smartphone. Again, you need to know what pieces of art you want to see because it is gargantuan, and the placards are hard to see. Seriously, the Pitti Palace complex is over-the-top enormous. Your legs and brain will be on overload. Don't skip the Treasury. The gardens took us at least another hour. Very restorative. You could spend several days just at the Pitti museums (I think there are 5 there).
The second and third tier museums of Florence are not crowded, and in any other city, they would be the star attraction. Consider these two for a change of pace:
Museo Marino Marini, free, near Santa Maria Novella, has wonderful architecture and modern sculpture (lots of horses), giving a needed palate cleanser from Renaissance paintings. A friend who is an artist made sure we went there. Good call. Allow 30-60 minutes.
If you care about science at all, go to the Galileo Museum, near the Ponte Vecchio. The Medicis funded Galileo, so his scientific instruments are also works of art. As the galleries go on, you work through later centuries of science, even getting some hands-on demonstrations. Allow 30-120 minutes, depending on your interest and energy.
We LOVED our trip to Florence.