Let me start by saying I've never been good at hawking myself. "Let the work speak for itself" has been my motto.
Well times change. Two years ago was an eon in digital publishing and the clammor for attention is fierce now. I do feel somewhat sorry for readers. If they're scrolling through a list of a couple thousand books, how can they tell the quality from the dreck. And there's plenty of dreck.
Obviously a less than professional cover is a quick way to tell. Then the potential customer should read the blurb and then the sample. It's very time consuming.
I feel sorry for writers because even drecky writers can pay to have a pretty good cover done for them. It doesn't improve their writing any but there you are competing with them. Everyone shouting for attention.
It's rather demoralizing when you think about it, isn't it?
I just read what happened to Cora Carmack. She wrote a book, self-published it and within 2 months was on the NYT bestsellers list and had a high 6 figure book deal. There's always going to be an outlier but she proves you can be heard over the crowd. What makes her such an outlier is that it came so easily. (Putting the book aside.)
Amazon search engine looks at all the words in your "Look Inside"/it's all metadata, so let's put that aside for the moment.
If all writers who haven't made it to the top of the charts are equally unknown, and equally doofusistic, if you have a legitimate horn--toot it. Have you achieved anything? Let the customer know. Have you won an award? And I don't mean a badge in Girl Scouts. Let's tout real achievements and I mean real, not fantasized or invented ones because someone may decide to check just to prove you're fabricating your background. If you're writing a novel with a boating background and you sailed in an America's Cup race, say that in your bio and the blurb. If you have special skills or talents, mention that. Make yourself look as bright and shiny as possible. Rinse and Repeat as necessary. Don't annoy people but remember that new customers are always entering the market and you are an unknown to them.