Amazon doesn’t “push” books unless it is their own imprint or you pay to play via AMS, which is spiraling out of practicality for ROI.
Sales build sales. Reviews help. Email lists are nice, but unrealistic to get people to sign up for them, especially these days.
Frankly, I’ve seen all the advice about email lists and Facebook and twitter and all of that. And I do it all. But bottom line the best thing is write a good book. Then? Write another good book.
The odds of an indie author making it these days (and making it is different for everyone) are low; same as getting trad published. Maybe even less.
Bottom line? Write. Then write some more.