There isn't much that individual consumers can do to right the economic balance between the developed world and the developing world. Promoting sustainability in poorer regions basically amounts to paying local producers higher prices for products they export than what they are getting, something that multinational companies, which usually do the exporting, are not prone to doing. Given the gulf of distribution that separates the average housewife in Chiba and the average tea plantation worker in Sri Lanka, there's very little the former can do to directly help the latter.
Except buy Fair Trade-labeled products. Various world organizations certify producers who guarantee, among other things, that their employees earn a decent working wage and give them some say in the operations of the farm or factory. Thus, when that housewife buys some black tea at her local Ito Yokado with a Fair Trade label on it, she can feel assured that more of her money is going to the people who produced it rather than a host of middlemen-multinationals.