Publishing in a new journal in Africa is the best way one could contribute to growth of publishing and literature in Africa. the other ways are being a reviewer or editor and of course, using literature from Africa to increase citation scores of others, and in turn increase your own citations scores.
Sadly, in some cases authors target the so called globally indexed, high impact journals. These are journals published by the domineering publishers and indexed by policing organisations. The major indices, for example Scopus and Web of Science are owned by the publishers.
As a publisher, we strongly recommend that you send your article to an African journal even if it is new or not indexed in Scopus or Web of Science to help journals grow. If a journal does not receive manuscripts, it will not grow. All the journals that are now indexed in Scopus or Web of Science started in the same way, journals need support to grow. You can support them by submitting papers before they are indexed. The journals that are indexed now, were grown by those who submitted to them when they were young.