There is this narrative going in Nigeria – to give apps free or to charge for it. The answer is very difficult. Why? Making is free may not be sustainable. You can be out of business after a certain number of months. Asking for premium, the payment system is still primitive for it to work.
So, which one is better? Both. It all depends on what you need to achieve. Understanding that Apps is still at infancy in Nigeria, it will be very difficult to command that premium price they enjoy in the developed world. But getting your name and brand out could be more important. In that case, the App can be made free.
However, it is important that you watch how the business is developing. If you continue to make it free, you can simply destroy the market. Others will be unable to sell and you guys will have problem. The right idea is to gauge the state of that sector and ascertain what is the best strategy at that moment. While it makes sense to make health apps free in Nigeria to get customers, it may not make sense to make bank related apps free. You examine the purchasing power of the users and the best model to use to get market share, press, etc depending on your objective.
But note – Nigeria is not U.S. and it is possible that you cannot get anything out of the freemium. While in US, people will come and invest as you build user base, in Nigeria, that may not happen. The people with investing resources who did not make their money through business may not care. So that said, think very well before you release that app and make it free. A free service does not grow revenue. Without the latter, business cannot survive.