So you want to sell all the books. Me, too, my friend. Me, too. Heaven knows I've chased my fair share of strategies and secret sauces that led me to one conclusion: You can spend your life chasing attention.
You can spend all your time and all of your money on classes that promise to teach you The Secret to selling millions of books. Facebook ads! No! Amazon ads! Tik Tok! Newsletters! (Of surprise to no one - blogs never seem to be on the list of 'The Secret to Selling -- Anything.') But the truth is much harder than any of the 'experts' who can teach you to market your books for six easy payments of special for you today want you to believe. The truth is that platforms can be carefully created and nurtured, but they are also very much a function of how well your stories fulfill reader expectations and of luck. One you can control. The other you can't (but you can help it along slightly.)
Reader expectations are knowable and writers can opt to ignore them or make sure their stories hit them. If you're writing a sex scene in a romance novel, you'll write one kind of scene. If you're writing a sex scene in a horror novel, the sex scene will have a very different feel because it serves a very different function - and you're doing it that way because you know that a horror novel needs to read and sound and feel different than a romance novel.
As for helping luck along, I'd like to tell you to just see Jeffe's post because, yeah. What she said. The very best advertising for your current book is your next book. And the best advertising for your next book is your current book.