Interrailing Eastern Europe this July (20+ days)

I am looking to go interrailing this summer majorly in central and eastern europe while avoiding tourist hot-spots in the Western Eu. I am planning to start in the beginning of this July. Pretty flexible as to where we go and might do a loop around Eastern Europe starting from Berlin ending in Austria. I have got a draft for the route to be taken to go all the way to Istanbul and back again. Some places which I would like to go to would be Berlin, Krakow, Prague, Istanbul, Belgrade and Vienna. However, I do realise that this may not be everyone's cup of tea so my trip is totally flexible. I am looking around to see if there is anyone who want to join in this exploration and I don't have specific requirements as to who I travel with as I'm sure any company will be great company!