Definitely post this on the lonely planets thorntree message board as there are more backpackers there

The part about Greece looks okay. Mykonos is an expensive island, but there are spaces for backpackers at Paradise Beach: http://www.paradise-greece.com/accom.html. July is quite busy, so you would need to book in advance. To see what goes on there check out "paradise beach mykonos" on YouTube.

Three days in Athens is enough to see the main sights and a few museums. There is a backpackers hotel in central Athens, but I can't tell you much about it.

Don't forget the fantastic European train system and if you are under 26 you can get the bargain Eurail Youthpass - a pass for unlimited travel for X number of days in a ;longer period or a consecutive-day pass - hop overnight trains say from Paris to Barcelona or Barcelona to Paris, Madrid, etc and save time and also the cost of an overnibght accommodations.

Overnight trains run all over Europe and there are overnight ferries between Greece and Italy too.

Anyway to see sometrhing besides airports, tarmac and big cities consider taking trains as well and see some of the Europe between the big tourist cities - check out these IMO fantastic sites for learning a lot about European trains - www.seat61.com; www.ricksteves.com and www.budgeteuropetravel.com - download the latter's free and IMO superb European Planning & Rail Guide for lots of suggested rail itineraries in various countries (http://www.budgeteuropetravel.com/id2.html).

The time of year you go can make a BIG difference in costs - cheaper hotels and hostels can be much harder to get when Europeans tend to travel in droves, like during July and August in southern Europe - May, early June and September are fantastic times with good weather and far fewer crowds (and shorter lines to get into museums, cathedrals, etc.

If you could use your expertise and introduce me some amazing places that i absolutely should not miss out on please advise me! I will be very very grateful.>

well what are your interests? museums, cultural things, night life, natural scenery? That would help answer that wide-ranging question.

Hello russwongg!

You may want to share a bit more in order to help us help you.
First of all backpacking means differen tthings to different people. Usually by backpacking most people mean low budget but how low is low and what type of accomodation are you after? At least fom Greece, I think early July to late July makes a great difference on prices and crowds, so if you could share when you plan to come over, that would help too.
What kind of activities are you interested in? PalenQ makes a good point. Hard to advice without knowing your interests!

A couple of notes: Mykonos is not a beach it is an island. It is a 30 minutes or a 3-5 hours ferry ride from Athens area. It is a scenic island with many nice (mostly sandy) beaches but a very busy and expensive island. Sort of a posh place in high season. Lots of nightlife options too.
What kind of beach are you after and is there any other specific reason you chose Mykonos?
France is a country. Do you have in mind a specific location? Why you want to go there? You could spend your whole 25 days only in one country and still not run of places to see/things to do. Your itinerary is very wide, especially at this point.
Ending up in Barcelona, what is your aim to do there? Using it as a departure point or explore the city or what?

"France is a country..." Those comments apply to Italy too of course!

any backpacker will greatly benefit from having a copy of Let's Go Europe along with them - written by college students for younger folk - great coverage of accommodations - the ups and downs of so so many places.