Traveling across Europe - Group Travel

Traveling through Europe is something that I have always wanted to do. My plan is to take a semester off of school, so the trip would have to be from September through December. I am pretty flexible other than the time that I can spend abroad. Since it is almost a year from now, I haven't planned specifics and I am open to any ideas. The list of countries that I have on here are the ones that interest me the most but I am open to whatever. Obviously, it is not possible to travel all of Europe in such a short time without it being outrageously expensive, so if it is between western and eastern Europe, I am verging on the side of Eastern Europe. I am looking for a few trip partners who are open to change in plans (open to some spontaneity.) I am a college student so I am running on a tight budget and so staying in hostels etc. would be my first option. I am open to doing/seeing anything, but I would like to get a taste of the culture in the areas that I go to. I am not very into the tourist attractions so if that is what you want to do, this trip is probably not for you. I would like to experience the local cultures of the places that I go to, if that makes sense. If anyone has any ideas or suggestions, feel free to post them...I have never traveled across Europe before so I don't have a solid plan yet. The more I research places, the better of an idea I will have but I wanted to post a trip before I have details anyway just to see if anyone is interested!

Traveling across Europe