Who was the first recorded African Christian? What kingdom did he represent?

Answer 1

A eunuch minister of the Queen of Ethiopia, according to Acts 8:26ff

Unless you count some of the 3,000 of the crowd who were reported converted at pentecost, where Libyans and Egyptians were described as having being present.
Acts Ch 2

Answer 2

The Ethiopians have a very ancient Christian tradition that dates back almost to biblical times.

Indeed there is a strong tradition that the Ark of the Covenant is in a monastery in Axum in this country.

Answer 3

The Ethiopian treasurer, supposedly converted by Apostle Philip. (See Acts 8.)