This list keeps on changing but as of 2015 following is the list. Criteria is GDP PPP as PPP based GDP is more sensible then just GDP. As cost of any good is not same in all countries so GDP should be adjusted to purchasing power parity...
Rank Country GDP Per Capita (PPP)
1 Malawi $226.50
2 Burundi $267.10
3 Central African Republic $333.20
4 Niger $415.40
5 Liberia $454.30
6 Madagascar $463.00
7 Congo, Dem. Rep. $484.20
8 Gambia, The $488.60
9 Ethiopia $505.00
10 Guinea $523.10