First timers! 10 day itinerary help!

Generally, Rome-Florence-Venice makes a good 10-night trip. Definitely cut Positano. You might be able to fit a day in the Cinque Terre, but is it worth it?

Train schedules will be fully loaded by June 12.

I agree with Sam, you're trying to bite off too much. Five of your ten days will include moving between places, which takes time. Maybe six of your days, if you have to spend one getting back to Rome for your return flight. Lots of taxis, stations, and trains on those days.

Are you sure it's really "more economical to fly round trip"? Keep in mind the added cost of backtracking to Rome, and the value you place on your limited time. Use the "multi-city" setting on airline websites and search engines -- usually it costs only a little more to fly "open jaw" like that.

Doing all of that in 10 nights is going to be exhausting. I would highly recommend investing in a little higher airfare to fly open jaw: into Venice and out of Rome. Otherwise you'll be spending too much time (and money) on the trains.

The website Rome2Rio is great for figuring out the best way to get from one place to another. Good train information also in the Man in Seat 61 site. https://www.seat61.com/ Others on this site have explained the intricacies of Italian ticketing for different classes of trains.

You really have to balance your appetite/energy for seeing a lot vs. your tolerance for whizzing past and not really experiencing BEING in a place. In a 10-night trip, you'll likely need a day to do laundry and take care of other personal business. Also, when you're touring at a breakneck pace you're more likely to overspend because you don't have time to consider every decision involving opening your wallet.

Italy is beautiful just about everywhere. You can't go wrong, IMO, except if you deny yourself time to enjoy and appreciate being there.

Start by being honest with yourself. Do you really have "10 nights"?

(Hint: most people start off by telling themselves little white lies about how much usable time -- not counting travel days -- they actually have, by counting "days" starting when they close their front door at home and counting until they return. That may be how long your trip is, but that's NOT how much usable time you have in Europe. Don't make that mistake, especially on such a short trip when ever day counts).

Step One: Post specific dates of your travel, including flights (if you do not have flights nailed down yet, then post proposed dates). Without actual dates, you can't make rational decisions.

Also agree that you should take a sober look at whether it's actually "cheaper" to fly round trip. Apples-to-apples, I suspect not. But there's a bigger issue there: your most constrained commodity is "number of days in Europe". Even if it costs you a few more bucks to fly open jaw, doing so would effectively "buy you" extra days. On a very short trip, that trumps a small difference in monetary costs.

Remember that your first and last days of any trip are essentially wasted. And every time you move to a different city, it's also a lost day. If at all possible, try to make your trip a few days longer--like 2 weeks and some weekends.

You're wanting to visit some very important cities, and those that are worthy of more than just a day or two. Rome itself is a 7 day city.

Like they say, value is not just flying with the cheapest airline. You've got other things to consider. For example, we prefer to get into Europe mid-day--and not 7:00 a.m. That way we can get into our hotels quicker, catch a nap and be ready to hit the town that night. Nothing worse than having to spend 7 hours carrying around your luggage in a strange city. Come to think of it, Venice is a tough town for luggage anytime of the day--with all the steps and bridges.

I usually will run by the train station the day before we plan to leave and pickup the tickets then. I may be leaving some discounts on the table, but by then I will know when and where we want to take the train to.

I believe in mapping out what your days might look like, based on where you are sleeping. Something like this:

Night 1, Sleep in Venice. Arrival day
Night 2 Venice. Sightseeing in Venice.
Night 3, Florence. Travel from Venice
Night 4, Florence. Sightseeing in Florence
Night 5 Rome. Travel from Florence
Night 6 Rome
Night 7 Rome
Night 8 Rome
Night 9 Rome
Night 10 Rome
Fly home

Based on the above, you would only have one full day in Venice, one full day in Florence and five full days in Rome. I would NOT try to add another stop. Every time you change locations you lose half a day, at least. Between packing, getting to the station, travel time, getting to your next hotel, etc. And the above is based on flying into Venice and out of Rome. If you do round trip into Rome, you lose another full day to travel.

I KNOW you want to “see everything”. Everybody does. But do you want to experience what your seeing, too?

To repeat above advice
If you actually have 10 NIGHTs on the ground in Italy you barely have enough to meet the suggested minimum in 3 locations
Venice 3
Florence 3
Rome 4

Open jaw is the way to go but if it’s not feasible for you then head from FCO to either Florence or Venice by train on arrival. I’d go to Florence just because it’s closer, then to Venice then fast train back to Rome for your final 4 nights.

Tell yourself you will return, don’t try to squeeze in anymore or your trip becomes a whirlwind of trains, hotel check ins/ check outs with little time to enjoy the places you visit.

A 3 night stay means just 2.5 days in location for sightseeing. You need to account for checking out, getting to train, riding the train, getting from station to next hotel, checking in and getting oriented.
That’s a half day or more gone every time you change locations.

Be sure you are using the “multi-city” search function, not 2 one way tickets.

Trains will be easy, all direct fast trains between the 3 major cities.
Trains to CT, Amalfi, Tuscany will be more time consuming, not necessarily complicated but involve regional trains with multiple changes.
Tuscany actually really needs a car.

Use the official train sites, you can get an idea of options by using days comparable to your future days in Sept. Schedules will be posted June 12 for Sept.

https://www.trenitalia.com/content/tcom/en.html

https://www.italotreno.it/en

I am having trouble figuring out the train schedules, high speed, to see if this is even possible.

Even if you can logistically put together a travel schedule to get to all the places you list, traveling is all you will be doing. Is that what you want to do?

The original plan was to fly into Venice and out of Rome, but after looking, its much more economical to fly round trip, specifically from Rome.

Where are you? Hard to offer any help on that issue not knowing the 'where'

For all the reasons stated above, this is the itinerary I would use:

Venice 3. (will give you 2.5 days)
Florence 3 (will give you 2.5 days)
Rome 4 (will give you 3.5 days)

Try to fly open jaw (into Venice/out of Rome) if at all possible. If not, fly into Rome and take a fast train to Florence on arrival day; your order would be Florence>Venice> Rome. You could also do a Venice>Florence> Rome. In either case, you'll want to end the trip in your city of departure. IMHO, Positano is too far for a quality day trip from Rome, and not worth the time/effort for just one night either. While you could day trip to the CT from Florence, I don't usually advise it, and I personally wouldn't add 1 more hotel move to your itinerary.

That said, if you are not all that interested in what Florence has to offer, you could do (in this order):

Venice 3
Florence 2 (leave Venice early to make the most of your short time)
CT 1
Rome 4

As the CT is really time-consuming to get to from Venice, I'd only do this if you're putting Venice at the start of the trip and proceeding from Florence to the CT. If planning on visiting Florence's more famous museums, you'll need to be cautious that your one FULL day there is not a Monday when most are closed.