If you produce a FREE digital product, AVOID growing by buying users. Ad-driven revenue generally grows slower than customer acquisition cost (CAC). Where you decide to be buying users, you would run out of money in Nigeria. The most important thing for a FREE product is to make something really exciting which people would like to use and tell others to use [free marketing]. Paid acquisition of users for a free product in Nigeria would not take you very far despite any ephemeral buzz.
If your customer lifetime value (LTV) is less than N500k, do not build a sales team. Rather, focus on blogs, SEO, ads, etc to attract users, but structure the growth to recover CAC within 6 months.
But if the LTV is about N2 million, sales team makes sense.
So, if you look critically, it only makes sense to have sales team for enterprise products (consumer product is marginally a tougher call to make) in Nigeria. That does not mean you cannot build a sales team for a consumer product. Largely, the best model is to focus on having very great products which can sell themselves.