I think the single biggest thing that helped sell self-published books, beyond the quality of the work itself, was reviews. Relentlessly pursue book reviews.
Here’s how to get them:
Prior to launch, contact 75 people who will agree to be advanced reviewers, keeping in touch with them over the next several weeks, ultimately launching with 25 reviews on your Amazon sales page on day one. Enough reviews will trigger Amazon to begin recommending it to others. Your book also gains quite a bit of credibility in readers’ minds when they see more than a handful of thoughtful reviews.
Look up reviewers on Amazon, Goodreads and Audible on an ongoing basis, and actively reach out to these individuals to provide a review in exchange for a complimentary copy of the book. Many people will take you up on this offer. This is tough, tedious work, but well worth the effort. I have been approached by several authors and am more than willing to do this.
Finally – run free giveaways of book copies. Engaged members of Goodreads will be willing to review for free copies.
Regarding exposure: be sure to spend time networking with whoever you can, and investigate genre websites, and reach out as much as possible to offer guest postings, interviews, book reviews, or whatever you think that site might find interesting, or live readings at physical locations like libraries.
You may not get many of these opportunities, but it will certainly help you sell books.