You could spend an awful lot of time on gimmicky promotion - but ultimately, unless you are either exceptionally gifted or exceptionally lucky, it's not going to pay off.
If you want people to buy your book, you need to find a way to advertise in front of people already interested in buying a book, and given them a reason to look at yours instead of any other book (including bestsellers).
So if you are going to spend time on marketing, you need to be very focused on targeting:
- the right group of people (ie, readers)
- who are already open to buying a book
- who can be given a reason to buy yours
So far as I'm aware, Amazon Ads is going to be the only platform that might be able to deliver on this - with one huge caveat: you will likely lose money if promoting a single book.
My experience running marketing campaigns is that it would be exceptionally difficult to successfully run a campaign for a single product.
Ideally, you want multiple products - ie, alternatives that might suit better if the first isn't enough, else upsell through someone buying the first book and then wanting to buy sequels.
Which means you already need those sequels published.
Simply put, the best way you can market your work would be to write multiple books - the more the better - with some working as a sequel (ie, a trilogy) with others perhaps in a different but related part of the genre (ie, epic fantasy to science fiction).
Only then - when you have multiple books - do you then consider any form of paid marketing campaign.
In short, writing lots of books is going to be your best marketing strategy.
This opinion comes from:
- my own experience running a marketing agency
- my observation of how traditional print publishing works
- my observation of how many self-published authors now work.
Hope that helps.