To get real traction on your game downloads on Google Play store, you need to be Featured by Google on the front page. To be even considered by Google for a possible Feature, you need to either:
1) Have at least 50,000 downloads and a 4.5 star rating, or
2) Know someone at Google Play (and I don't mean the janitor).
To get to 50,000 downloads, you need to already have a dedicated customer base that rushes to download your game, or you have to build your niche from scratch.
I don't thinking building your niche around an African audience is a bad thing per se as iRoko does that and are quite successful. You just can't focus on Nigeria alone. iRoko again only has 6% of its users in Nigeria. The focus should really be on the sophisticated Africans in the diaspora with more disposable time and income.
To get to those guys however, you will have to go through the same advertising channels the big mobile publishers (King, Gameloft, etc) use. To make matters worse, the big console publishers (EA, Activision, Ubisoft, etc) have now entered the mobile space, so acquisition costs for users have gone through the roof!
I think one way to make decent returns is to work out a publishing deal with one of the publishers. Gamsole does that with Microsoft and Chillingo offers publishing services as well. That way you can focus on building a solid product and leave the advertising and marketing to someone else.
But I feel you guys' pain. Funding and technical resources are always a hurdle. I can only imagine what it's like working in naij (Lagos to be specific) with the insane traffic, insane prices for passable internet, and insane Nepa situation. I guess the latter two can be solved by getting a membership at CcHUB or something, but that Lagos traffic mehn....no forgiveness.