I think subsidies alone are not the best solution. If the developing countries are just supported by funds alone it does not work effectively. They need to be driven in the right direction; they need plans on how to improve their whole political system, trade system and so on. They need a real development plan and also a team of experts, which help during the time of introducing changes and be a contact person for questions.
Another option could be trade advancement, e.g. all poor countries should be given non-restrictive access according to export. That should help to earn additional income beside the products which can be sold whitin the country.
Beside this, the contraction of debts should be driven faster on, like previously said financial aid. According to a statistic the public development aid decreased in the developing countries to 0,24 % of the gross domestic product, by comparison to the UN-goal of 0,7 %.
The advancement of private capital in the low income countries, especially as external direct investments, has two advantages: consistent finance flow and technology transfer - the important assumptions for a prosperous economy.