Financial talk

My friend and I are flying to Europe some time in August for two weeks. We have absolutly NO plans yet! We are open to anything. Neither of us have ever been and have no idea what we are in for. We want to fly as cheap as possible. Any advice on which city/airport to fly into and/or airlines to use? We are probably getting the global Eurail pass because we are both "youth" and that seems the best deal. We would love a good mix of scenic settings, historical points of interest/touristy things, local "spots", and lively drinking nights. We are currently thinking France/Belgium/German as focal points but are open to suggestions. We don't want to spend spend much money on lodging, will probably sleep on trains and try a few hostels. Any advice on that front is also welcomed!