Depends what you want to visit,what you like to do and when you want to come here!

You can get practically anywhere by train (or other public transport) here. 

The only real recommendation I have for people not used to travel by train, is to keep France and Spain a bit later in your trip. Cause it's a bit more "difficult" to travel there by train. With lots of mandatory seat reservations, that are a bit tricky to get. With a bit of experience, it'll go much smoother and it'll be less stressful. 

Just get a map and some pins then check out the man in seat61 website,

Your question is far to wide! My best advice is buy a guidebook to Europe and take it from there. Once you have some ideas of the places you want to visit the community will be delighted to help

There are several proposals on the main site, I think even according to interest and to how long time you have. Another thing is the money you have-prices in EUR can differ an awful lot between countries. The more east, the barato, the more norte, precioso.

Latino all tend to start in ESpana-also has plenty of cheap flites/vuelos. And the lingo is moreorless the same. And sad but true: yes, ES is by far the very worst country to use a pass. Blame RENFE. As geografy has it, you then always enter FRancia-#2 in worst for passholders. So go out of there asap.

Buenos viajes, porteno!