To make this more time/cost effective and to maximise the sightseeing factor my suggestions for your initiary are the following:
Dublin, Ireland
Belfast, Northern Ireland
Edinburgh, Scotland
London, England
Paris, France
Madrid, Spain
Granada, Spain
Sevilla, Spain
Barcelona, Spain (budget flight to Italy)
Rome, Italy
Florence, Italy
Venice, Italy
Salzburg, Austria
Vienna, Austria
Prague, Czech Republic
Dresden, Germany
Berlin, Germany (budget flight to the UK or Ireland, fly home from London or Dublin)
I cut out a few places because:
Monaco is nothing but an ugly and very expensive accumulation of concrete.
Pisa can be done in half a day, there is almost nothing there but the leaning tower. Not worth it going there unless you got a budget flight to or from the nearby airport or are coming through on your way to Cinque Terre.
Milan - expensive city with not really that much to see compared to other cities. Between Milan and Florence Florence wins hands down.
Swiss Alps are very expensive, not very conductive to travelling on a budget.
The places I added are either a total must or make a convenient place to see enroute. (Dublin to Edinburgh overland is usually done via Belfast with the ferry from Belfast to Stranraer.)
It will take you about 65-70 days and around 3500-4000 EUR plus the cost of flights to Europe to do this initiary.
If I was you I would warn your parents and relatives beforehand (like right now) that you plan to travel to Europe after graduation and ask them to finance your flights and maybe a 2-months Eurail pass as a graduation present. With the flights and the Eurail pass paid for plan on having around 40 EUR per day for food, accomodation and fun things to do (2600-3000 EUR). This is the money you need to save up between now and your graduation. Best time to go would be May/June or September/October. In September/October I would add in Munich (Oktoberfest!) and maybe reverse the order of travel (so that you are in Southern Spain and Italy near the end of your trip). If you go July/August it will be high season, the flights will be very expensive and it can be difficult to get seats on buses and trains, so it makes more sense to go before and after.
[ Edit: Edited on 16-Aug-2009, at 02:48 by t_maia ]
, as well as stay in hostels and such, so long as they are relatively safe, in order to reduce costs as much as I can. I plan on staying anywhere from 3 to 5 days in each city mentioned (if recommended), so counting the number of cities, this will be quite a lengthy trip.