itinerary ideas/suggestions

Always add as many days as you can. You are tentatively planning only one full, non-jetlagged (you hope) day in Venice, which I think is too short. You are allowing only two full days in Florence if you stay through Night 5. I like Bologna a lot, but you can't afford to make that stop, and in any case only a few hours there would be sort of silly; it's a 20-minute walk from the train station to the largest medieval center in Europe.

What do you want to do in Naples? Aside from the city's sights (the Archeological Museum seems important), there are lots of side-trips people think of making from there. You'll only have 2-1/2 days available. Will that be enough for what you hope to see? A lot of the side trips probably require a full day.

Have you checked airfares into Venice and out of Naples? It all depends on your point of origin, but for me that would be a much more expensive combination than Milan and Rome. Which doesn't mean you shouldn't use Venice and Rome--just that I'd check on the fare sooner rather than later.

I agree with what acraven said, as usual. As it stands, you're only going to scratch the surface of any of the places you will be visiting. And each travel day means only a partial day in your arrival city by the time you travel, get to your hotel, and drop your bags. And as for your arrival day in Venice- unless you are travelling from another European country, you should factor in jet lag in any other activities (besides just walking around).

If you can add extra days, then do it. Figure out what it is you want to see and do in each place. Make a list. Then spread out those extra days accordingly.

I'll agree with above-add as many more days as you can. As you have it now you are trying to cover a huge distance with 4 major cities in what looks like just 12 nights?
Count your trip in NIGHTS, not days. A 2 night stay means you have 1.5 days to sightsee, that's not much at all for major destinations.
Venice needs 3 nights if it's your entry point, Florence should get 3 nights minimum- add 1 more night for each day trip you want to take from there, Rome needs minimum of 4 nights

If this is your first trip you can't go wrong sticking with the big 3- Venice, Florence, Rome. Spend a few days exploring Tuscany hill towns with a car or as day trips from Florence.
Not sure I'd add Naples to that trip. If Bologna interests you then give it at least 2 nights and drop Naples

Our first trip to Italy started out with just 12 nights, I thought that would be plenty til I started researching- we ended up with 17 nights we were limited only because my husband was not yet retired- otherwise it would have been more.

We did
Venice 3
Florence 3
Tuscany/Assisi- 6 nights
Rome 5

Make your list of must sees THEN figure how many nights in each location- allow some free time, when will you eat gelato?
Be careful with Florence- Sun/Mon are difficult there as so many sights are closed. I would think you can still use current guide books to get an idea of open/close days/times whereas this year we must use the actual websites to check for COVID related changes..
When you research flights do try to fly IN to Venice- much easier than out of. and it does make a great get over jet lag place.

Not to pile on but I agree with all the above.

It would be a shame to go all that way and only remember the transportation...

I'd suggest fewer places, slower.

Ditto to all of the above: too many places for too short a time.
Add as many days as you can, and maybe look at a few day trips (the folks here can make suggestions) if you think you can't fill your time just in the "Holy Trinity" cities (Venice, Florence and Rome) themselves. Don't short them, though.

I'd for sure drop Naples and save it for another trip when you can do the Sorrentine/Amalfi coastal regions as well. You asked for ideas for Florence? That's where it's up to you and a good guidebook. There is a LOT to see in Firenze if you enjoy what it has to offer! Being we don't know your interests beyond "typical tourist" stuff - which is sort of a fuzzy area - marking what you two see in a book that trips your triggers is a good place to start.

More days will give you the opportunity to explore beyond the mobbed, most-visited attractions + provide some welcome breathing room. If crowd levels increase to near pre-COVID levels next year, being in the middle of them all the time would feel "hectic" enough without managing a rushed itinerary on top of it! :O)

Drop Naples and spend more time in Rome

If you add 3 days, you should have 17 days, 15 nights. See if this itinerary would work for you.

Day 1. Travel.

Day 2. Arrive Venice.
Transportation. https://europeforvisitors.com/venice/articles/venice-tourist-travel-cards.htm

Attractions to visit.
https://www.venetoinside.com/attraction-tickets-in-veneto/#VENICEMUSEUMSANDMONUMENTS

Day 3. Venice.

Day 4. Venice.

Day 5. Train https://www.lefrecce.it/msite/?lang=en#

(2H13m) Venezia S. Lucia- Firenze SMN Or stop on the way @ Bologna, spend 7-8 hours then 37 min train to Florence.

Attractions http://www.b-ticket.com/b-ticket/uffizi/default_eng.aspx

Day 6. Florence.

Day. 7. Florence.

Day. 8. Florence. Day trip to Siena. Bus 1:17m.

Day 9. Train Firenze- Roma Termini (1H35m)

Attractions . https://www.coopculture.it/en/circuito.cfm?id=4

Day 10. Rome.

Day 11. Rome.

Day 12. Rome.

Day 13. Roma Termini-Napoli Centrale (1H10m

Attractions

https://www.timeout.com/naples/things-to-do/best-things-to-do-in-naples

Drop your luggage at the Kipoint luggage storage in the station and take the metro (Map)

https://www.napoliunplugged.com/naples-consolidated-metro-map

to the Archeological Museum. Then wander old center of Naples. Metro back to the station, pick up luggage. Take the Circumvesuvian to Sorrento.

https://www.sorrentoinsider.com/en/naples-to-sorrento-train-schedule

Day 14. Sorrento. Day trip to Pompeii.

Day 15. Sorrento. Day trip to Amalfi Coast.

Day 16. Sorrento-Naples 1 night Naples.

Day 17. Travel.

atiffany2401, I see that you're relatively new to the RS forum? A gentle reminder that we're not allowed to promote (in other words, post links to) our own blogs or businesses in the forums; see guideline #6:

https://www.ricksteves.com/travel-forum/community-guidelines

So by all means, share experiences and advice from your travels but best to delete the link to your blog & business in your post above before our trusty moderators do that for you. :O)

For a self-guided first trip IT tour, I agree with flying into Venice but I would not explore the Amalfi coast with less than two weeks to see ITs major sights. Instead, fly home from Rome. How about:
Day 1 – arrive in Venice and get to know the area where you are sleeping.
Day 2 – visit St. Mark’s Square and Basilica and the Rialto Bridge. At twilight take a vaporetto water bus from one end of the canal to the opposite i.e., the train station and San Marco Square. You’ll see the Venetian palaces that line the Grand Canal and the giant crystal chandeliers illuminating its spacious foyers. The great thing about seeing it at dusk is you won’t see the decay on the exterior on these incredible gothic mansions.
Day 3 – get lost and when you’re ready to get back on the beaten path, find the crowd.
Day 4 – once I stopped in Bologna on my way to Florence and visited a major square and ate lunch afterwards. I don’t recommend this unless you research it before going to truly appreciate it. However, you can stop in Padua (Padova) instead and visit the Scrovegni Chapel on your way to Florence. You’ll need to buy tickets before leaving home. The town is also worth a stroll before hopping back on the train.
Day 5 – visit the Uffizi Gallery. Be sure to purchase tickets online two months before. Afterwards visit Accademia to see David.
Day 6 – Duomo Museum and afterwards visit Piti Palace.
Day 7 – take a direct bus to Siena for the day and visit Il Campo square and the duomo.
Day 8 – take a direct train to Milan for the day.
Day 9 - take a train to Orvieto and store your luggage and explore there before ending the day in Rome.
Day 10 – Colosseum and make sure to take a taxi at night to see it fully illuminated at night, it’s worth it. Capitoline Museums and Pantheon.
Day 11 - Vatican City (St. Peter’s Basilica and Vatican Museums).
Day 12 – nonstop train to Naples for the day and visit the Archaeological Museum and take Rick Steve’s Slice of Neapolitan Life Self-Guided Walk. You’ll need to buy his IT guidebook 26th edition. The 27th edition will be available in the fall’22.
Day 13 – fly home.

On our trip to Italy in 2019, there were places that I didn't plan enough time in. We did two nights in Florence and three in Venice which were definitely not enough. Four nights each in Rome, Cinque Terre and Paris was adequate. In retrospect, probably including CT and Paris was crazy. However, CT, midway in the trip, gave us some respite, time to let our feet rest and do laundry. We shopped and cooked and wandered. Refreshed, we enjoyed the second half of our trip more. As for out-of-the-way Paris, during the pandemic, it gave me a lot of comfort that I had finally been there. I'm grateful for every spot we went to and we're planning to go back again. I'm not sure you can ever spent enough time in any place in Italy and some will call you to return again and again. Listen to your heart.

Since OP has never returned after first post in July I’m guessing no longer looking for suggestions