It sounds like you've tapped your social media reach. 10 isn't unusual. Some are a bit better, some are worse. (Mine was zero. I don't mention writing stuff to my friends.) But basically, you're done there for now.
The best marketing you can do is to write and release a second book in a series in a popular genre. Then a third. (And so on.)
The next best thing is to get a cover that looks professional and looks instantly like your genre to a reader. (This however, can cost money, but it's the best money you can spend.)
The next best thing is also just costing time--write a compelling blurb that explains succinctly what's at stake in your book for the characters.
The next best thing really is best done prior to publication but it's never too late with self-publishing. That being--make sure the first few pages in your sample shine. Hook the reader quickly, whether through incident, prose, or character.
The next best thing is to find some way to build social validation through online customer reviews and this also only costs time. You don't want to fake or cheat your way to reviews. Stay away from friends and family. You want to get them legitimately by requesting reviews from bloggers or giving away free copies to readers who do reviews, and so on. Find a way. It's a long, slow build. (You know you signed up for a marathon, not a sprint, right?
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When you've done all that, you've probably reached a point where paid advertising can make sense. (There are outliers who've done it early and successfully, but never expect to be an outlier.)