In a word, local! 
The vast majority of the hundreds of startups that I engage with every year across the continent  are solving local problems. Identifying community pain points, sand in the national gear box or broad African use cases that can easily be solved with tech.  Mainly because the global players have not prioritized the continent. 
Examples such as Nano lending or insurance, low cost origination, lightweight transaction switching, simple “Uber” of plays  Etc. Even Jumia is an African e-commerce play heavily customized for the unique needs of the subcontinent.  So we are living in the niches. 
Very few have picked a major global use case and gone after it. Not none , few.  Yes there are a few African success stories like in payments, industrial automation, bulk messaging and micro financial services that have gone global with multi hundred million dollar valuations. But no unicorns. Yet.  
We will get get hyper growth with out scale and that needs a global presence.  So start local but end global.