I was wondering if it would be cheaper to buy train tickets before I leave for Europe? or waiting till I'm there? I plan on buying my night trains as soon as they go on sale before I leave home. but I was wondering about Rome to Florence, and Florence to Venice after i arrive in Rome? it will be about 3 days early. thank you for your help.
Which night train are you planning on taking, and when? These trains can get booked up relatively early, especially from about May thru September. And is that trip completely in Italy as well? That bears upon where you might be able to purchase those tickets.
As for the two journeys you do mention, you might still find some tickets on sale when you arrive in Rome, so try to make a ticket office one of your first stops to see if you can get a deal.