Your budget definitely depends on what kind of traveling you are doing. There are such a arrange of things to do in Europe you If you can specify a little more I can try to help you to budget...
Where in Europe are you thinking of travelling? East/ West/ North/ South? All over? Main cities that you would like to hit?!
I did a trip of Western E in 2004 for the summer for 5 weeks and spent about £1200 including flights. train tickets and well everything for the hostels etc. We started in Seville, Spain and worked our way up by train via Madrid, Barcelona, up the west coast to France. Travelled all along the south of France, Down Italy to Naples and back up again to Switzerland and then went via Paris back to London. It was amazing fun! almost 9 years ago