Where do most authors sell their books? Amazon! Great place, but does everyone shop on Amazon? No. Many avoid it for specific reasons. I think an author has to sell on Amazon but not with them exclusively.
Get your book into Barnes and Noble. With them it is easier to get your ebooks in than your print books.
Smashwords is another place you should consider. It has a wide reach and has many books at Barnes and Noble and available on other readers.
Kobo is one that is great for targeting markets outside the US.
Your own site is one most authors ignore or don’t think about. Why aren’t you selling your ebook on there? It can easily be done and in several different formats for each reader’s unique ereader.
You need to place close attention to the rules when you sign up with an outlet to sell your books. If you have signed up for KDP from Amazon, you cannot have your digital copy sold anywhere else, even if it is on your own website. Wait until you are no longer in that program while still selling on Amazon and sell other places. You’ll reach more people.