trying to figure out if we should get a rail pass for some of the travel, and if so, which part?
Itinerary:
1. Rome to Siena on 5/5/17
2. Siena to Florence on 5/14/17
3. Florence to Lucca on 5/26/17
4. Lucca to Monterosso on 6/5/17
5. Monterosso to Venice on 6/9/17
Tried to check point to point fares but the website only lets me set up 4 trips in succession on one inquiry. Anybody here have some suggestions for me?
Do separate inquiries. Oh, wait, are you looking at a railpass site? Rail passes are almost never economical in Italy.
Are you using Trenitalia.com? That is the site you should use.
Trips 2 and 3 can be accomplished by bus or train; bus may be more convenient.
Other trips involve regionale trains combined with fast trains. You can save significant money by buying close to 120 days ahead. Since you listed dates in your post, it seems you are okay with committing to a specific date. Nail down a time for super-economy (no changes, refunds or cancellations) tickets and be sure you don't miss your train. You may be able to buy the regionale tickets at the same time (enter your departure and destination as "Monterosso" to "Venezia Santa Lucia", as an example).
In Italy a pass is virtually never good value, advance purchase tickets are so cheap.
"but the website" - which website? You should be looking on Trenitalia, the official Italian Railways site: http://www.trenitalia.com/tcom-en
As these are 5 different journeys on 5 different days, you need to look them up (and buy them) one by one, not together.
Tickets are cheaper the earlier you buy (the cheap tickets sell out, leaving only the expensive ones). When you buy, you choose which train and the ticket will only be valid on that train - no change of mind allowed.
For example, Rome to Siena is now showing prices between €17.30 and €44 depending on which train. For some of the trains the cheap tickets are already sold out.
A rail pass won't be of any use.
Two of those journey are served by Regionale trains, which are very cheap (and don't allow for advance buying). Siena to Florence costs about EUR 9; Florence to Lucca around EUR 7,50.
And, as said above, other trips come with serious discount when bought in advance with Trenitalia.
Just giving a shoulder to the posters above; a pass is not likely to be a good value.
Italian trains are very reasonable to begin with, and you can grab price breaks on longer, fast-train journeys (reservations for seat assignments) by booking in advance. Tickets for shorter journeys on regionale trains (no seat assignments) are cheap and easily purchased the day of your journey. And yes, for the locations you're looking at, use Trenitalia.com to see schedules and prices.
As Zoe said above, Florence - Siena is more directly accomplished by bus, and Lucca may be as well.
1. Rome to Siena on 5/5/17
... book ahead for Rome to Florence segment only
2. Siena to Florence on 5/14/17
3. Florence to Lucca on 5/26/17
4. Lucca to Monterosso on 6/5/17
... take local (regional) trains for these trips - no need to book ahead
5. Monterosso to Venice on 6/9/17
... book ahead for Milan/Florence to Venice segment only (depending on your chosen routing)
Just a note: if you pre-buy a ticket on a fast train, then no need to validate your ticket. However, if you travel on a regionale train, then don't forget to validate your ticket prior to getting on. The validation machines are usually pretty easy to find. Failure to validate can result in a hefty fine.
