Originally Answered: Traveling alone in europe?
It depends entirely on the lifestyle you're going to have while there. Alcohol is more expensive in Europe as compared to the United States, so be prepared for that. The approach I suggest you take would be pre-partying if you're looking to get smashed and not burn a hole in your pocket. However, there are safety concerns involved with that, namely, if you're absolutely wasted and not familiar with your surroundings, that could end quite badly. I'm not here to judge either way - and I've done my fair share of partying overseas myself, so - but a good plan is to have a clear plan of exit while partying. It's best if you are staying within a reasonable walking distance of where you're drinking, and never get too drunk so that you can't play the sober game. If it gets to a certain part of the night where you can tell you've lost control of your faculties, take a cab back to your lodgings. If you're in a non-English speaking country and you don't speak the local language yourself and you're staying a a hotel/hostel, carry around a business card so that you can just hand it to the cabbie. Don't get in a cab with anybody else in it. Always take official cabs, preferably with meters.
And in terms of how much money you'll be spending, again, it depends. If you stay in hotels and eat in restaurants, as the other poster said, you're gonna drop bank even without the booze and cover charges. Hostels will make it cheaper. Couchsurfing cheaper yet... and if you couchsurf, you'll be able to meet up with some locals who will probably be able to show you around and offer a good time. I've had luck with it before. If you are looking to make partying the center of your exploits, save money by exploiting cheap lodging and eat out of grocery stores. I would recommend taking in at least one nice meal in each country you're in, though; food in Europe is quite excellent and you should experience it. But for everyday grub, well, let's just say that the Dollar Menu in London is called the "Saver Menu." If you have a student ID, that can make some things cheaper, though a lot of places will want one of the international student IDs, which you'll have to pay to get.
Basically, if you're staying at a group room in a hostel (roughly $25 a night on average), I would budget at least $75 a day. And that's if you're going the cheap, cheap, mmm-I-Love-That-Saver-Menu route. (It will also depend on how much actual travel you're going to be doing and where you're staying. Paris? Budget more. Bratislava? Cheaper. If you're doing a lot of country-hopping, you'll need to factor in the cost of that as well.) You might not spend that much every day, but it will average around that much, likely. Again, this assumes you eat super cheap, buy no souvenirs, and are cautious about how much you spend on booze. There are lots of factors that could change this budget.