How much money does it take to travel to a few countries in a span of about 6 or 7 months?

I'm going to be graduating from highschool soon and want to travel! What are the costs?How much money does it take to travel to a few countries in a span of about 6 or 7 months?With the drop of the American dollar you can get by on $2500 and that may seam like a lot.