How to pick train time from airport

Wait until you get there to buy tickets to Venice.

There is only 1 direct train per day at 1:53 pm. Take the Leonardo Express to Termini and get a direct train from there if the timing does not work out for you. Yes, buy the ticket once you are through Immigration and customs with your luggage.

This is asked quite frequently and you should go back through the forum for
previous replies.

But the bottom line is that it's a risk analysis and decision you have to make.

Considerations:

• do you have just carryon or checked bags
• are you in the front of the plane or the back of the plane
• can you use e-gates upon arrival to get through immigration
• what are the terms and conditions of the available ticket options
• do you think the flight will arrive on time or even early (I realize there is no way to know this, thus the risk tolerance question)

Most people will say to wait and buy your ticket after you arrive, this makes
sense if price doesn't matter and the train won't sell out.

At the least, I would allow 2-3 hours.

I don't think there are that many direct trains to Venice, so your options may
be constrained anyways.

As mentioned I'd wait to get ticket. I fly into Rome from Charlotte but have an Italian passport... the line can be quite long for non EU passports. I buy my ticket as soon as I am through the customs area or on the Leonardo Express to termini.

The full fare is 92€ per person from Rome Termini on standard class (the cheapest class)..
If you buy early you can save about 50€