It depends on where you're planning to go, how you're getting there and how rough your willing to live. A lot will depend on the extras such as going out for a meal every now and again. Or how much you drink.
Some extra expenses are worthwhile such as going for a pizza in Italy.
Some sights are expensive to get into, but that's why you've gone travelling, there is no point in travelling somewhere and then not doing anything because your broke. If this seems like it is beyond your budget maybe you should consider a Working Vacation . Forget travelers cheques. They are safe and get better rates than cash but a hassle if there are no banks available and you may have to pay a fee to cash them. Occasionally cards seem to cease to work for a few hours but the problem seems to resolve itself before you starve on the streets.