How much money to travel Europe?

My sisters and i are planning to travel to about 10 places in Europe next summer for three months (Ireland, Italy, Switzerland, Greece, Spain, France, Scotland, Germany, Poland, Austria). Now these places are not "for sure" yet. But it'll give you a rough idea of where we wanna go. We'll be backpacking and so that'll consist of staying in hostels and taking trains and maybe low cost air travel. We've never actually been out of Canada, so we're not to sure how much money we should bring. We were thinking of 10 thousand each which will come to 30 thousand all together - but is that to much? or to less? we're just not sure, so any rough idea of how much we should bring would be very helpful! thanks! [: