A friend recently published a non-fiction title through a major publishing house. It all sounds great — favorable review in the Times Book Review, reviews in other major papers, radio interviews, readings, etc. A month after the book release, I asked him how many copies he had actually sold. About a thousand, he said. He's maybe got another month or two before the window on this book is closed and the stores start sending back the unsold copies.
The nasty little truth, I fear, is that most books don't really sell, even with massive publicity far beyond the dreams of most lowly eBook author/publishers. That doesn't mean you should do nothing, but it suggests that your expectations should be aligned with reality. It could be that selling a couple hundred books qualifies as remarkable success, even if most of them go to your friends and family.