The best way I can think of to help a developing nation is to buy the exports of its domestic companies.
Foreign investment into resource extraction sends money in when the goods come out, but then it goes all the way round in the revolving door and comes right back out to pay the foreign investors. (Foreign investment in infrastructure at least leaves the roads/wires/pipes behind when the money goes.)
You want to help Africa? Buy African goods and services from African-owned companies, whenever they are competitive in the world market. Treat them like economic grown-ups, and eventually they will shake off the memory of living in their colonial power's basement apartment and getting a weekly allowance.
Stop sending free money. It just ends up fueling corruption and making local business less competitive.
Africa, like everywhere else, is perfectly capable of addressing and solving its own problems when outsiders aren't constantly intervening in its affairs.
They don't though. We should all be helping underdeveloped African nations reach a basic level of education, economy and healthcare so they can decide their own future in the world.
As it is, they're being economically suppressed.