If you want to change things and help developing nations, make sure those developing nations have added most of the value.
For example, you can buy fair trade chocolate bars, with beans bought from Ecuador at a "fair" price, whatever that means. But then the bars are made in Switzerland, or France, and the European country adds much of the value, and keeps much of the profit.
Kallari Rainforest Chocolate, for example, is a cooperative making chocolate, and they pick the beans in the lowlands and drive up to the mountains and turn them into bars, and then airmail it out.
If you want to make a difference, figure out where your money actually goes.