It depends not on which country is your home but which country offers the best exchange rates.

Since you have not listed either where you live or where you're planning to go we can't give you more specific advice.

But here's some general advice.

Usually the richer a country is, the more expensive money changing is.

Developing countries often want major foreign currencies like USD and EUR and will offer better rates for them than you'll get buying the foreign currency of a developing country in the US or Europe (or Australia or Japan etc).

Places with a black market can sometimes offer even better than official exchange rates for the big currencies so the dodgy money changers on the corner can give better rates than the banks or official money changers. But as their dodgy know your numbers and don't get scammed!

If you want better advice tell us where you're from and where you're going (-: