The Venn Diagram with good writers in one circle and skilled marketers in the other doesn't overlap much. I realized, though, before I decided to do writing as a career I realized it: writers have to do marketing. They have to. Their careers depend on other people participating. In order to do that, folks need to know that a writer's doing anything at all.
It's damned hard. Marketing makes as much sense as a staircase into a blank wall. Writers spend all day long writing stories. That's private, it's wearying, and it's time consuming, and once it's done a given writer wants to do one thing and they definitely don't want to do another one.
The thing they want to do is spread that story around. Writers are contradictory animals. We're shy, but we also want our stories to get a lot of attention. There's a psychotic break there somewhere. Not sure exactly how that works, but it does. We want to tell stories to people.
The thing we don't want to do, like at all, is take on a second job. For most of us, writing is already our second job, after whatever it is that's paying the bills. Then writing. For a lot of writers, especially early in their careers, that's two jobs already. Job A pays the bills, Job B is writing. Odds are good that Job A isn't already marketing, and odds are even slimmer that Job A is marketing for yourself. The headache is that marketing is a deeply complicated, weird monster, requiring a degree of expertise in order to tame it. While doing marketing right for one client (one writer is one client, see), isn't necessarily a full-time job, it's definitely a part-time job. And you can't learn just some marketing, so you need to fill your head with a lot of weird terms (algorithm, PPC, ad-spend, ick), no matter how much marketing you have to do, you have to learn how marketing works.
So review: A writer, early in their career, has two jobs already. Job A that pays the bills and causes headaches. Job B pays no bills and causes bigger headaches, even if it does justify the title of writer. In order to make Job B into Job A, writers need Job C.
In the end, the question is: where are the shortcuts?
Now, the most important thing anyone wants to know is how to cut corners and skip steps in the more necessary tours on their road to success. Don't deny it. You know you're one of them.
There are a hundred punters on the internet who'll tell you that there are no shortcuts. All the corners have already been rounded for ergonomics.
Which is true.
It's also not true.
Here's the thing: there is one shortcut. Only one. There is one hack that speeds up the process, and only...well, actually two hacks. One hack is a sack of cash. The other hack, though, is much cheaper.
This hack is powerful, and it only works at beginning stages of any marketing endeavor. Because marketing is cyclical, it has a lot of beginnings, so you can actually use this hack a bunch of times. Just put it in front of your eyes and build.
Here's the hack:
Figure out someone you like and talk at them. There's a lot of advice out there about figuring out the target demographic for your book to tell agents or whatever--advice that's fine and dandy. This advice is not that advice. It's related, but it ain't the same. For one thing, not all your books will appeal to the same demographic; for another, you yourself might not appeal to the same demographic, precisely, as your book. So this isn't advice about demographics.
This advice, this hack, is about creating the marketing for yourself. That means for your books too, since that'll be the main thing you'll be doing when you get that far. In the initial phases, before your book has an audience, you will have to start one yourself.
You don't need "fans," whatever those are. That's the good news. Which is why this isn't a question about demographics.
You do need a solid core of people who believe in what you're doing. You need a tribe.
The internet is fat with advice about all the technical glamour and tools of marketing. You will discover a bewildering chorus of schools of thought all claiming to have the next great formula and quick fix that will guarantee your marketing success. And they are all both lies and completely reliable. Lies because "quick" means either expensive or ineffective when rushed. And entirely reliable because the tools of marketing, while they are headache fuel, are well established, objective, and (when you get to know some of them) intuitive.
Take any advice that makes sense to you. Arm yourself with knowledge. As you do, recognize there is one effective shortcut: talk at the one, maybe two, people you like. The reasons you like that one or two people are reasons shared with enough other people that you can build a solid corp of your tribe around them.
From that solid root, you build. It won't be fast, but it'll work.