So back when I was involved in publishing I did produce a best seller...and I hated it. So I'll give my two cents even though this thread is like 90 years old by this point.
1. Write your story.
Just write it. Doesn't matter if you know the plot before hand or not, how you write it is up to you regardless of what anyone says. If you like traditional writing conventions then good for you, if you don't and you feel your own style works better then good for you. My mentor (a publisher) once complained that people would edit the most interesting parts out of their stories trying to "fix" it or "improve" it when in reality they were just taking the elements that gave their stories flavor and a unique identity and cutting them out because they were scared of being different when being different is what gets you recognized. Don't let that be you. Write your story.
2. Practice your writing.
Make up prompts, look at movies, tv shows, anime, manga etc and try to describe scenes using your words. Copy a book word for word to understand how they author is using structure (sentence, scene, detail etc), write short stories. Practice makes perfect.
3. Ignore your doubts.
You will, at many points, have what's called an Inner Critic when you're writing. It sounds like "That's stupid!" or "Don't do that!" or "Can I really do this?" etc. It is simply the culmination of your doubts and fears trying to get in your way because it's a way for your brain to try and control for potential pain or disappointment. I can tell you without a shadow of a doubt that even the most poorly written books will find an audience (I've seen some of them), you've little to worry about if you give it your best and actually make an effort.
4. Show don't tell.
People make this rule a huge deal and it is, even I do it. Truth of the matter is that there will always be times when it's either necessary, acceptable or just outright more convenient to just say something. Understand something, your main goal as a writer is to put your audience in a trance where every word flows into their mind without conscious effort. To avoid breaking this flow, you will sometimes tell and not show and it's fine. Your audience will not notice it if you do it appropriately nor will they care. If you don't believe me, go look up the huge number of books that sell really well that have the words "His blood boiled" in them. Boiling blood is just a fancier way of saying "He's mad" and people float right by it just because it's so quick and to the point.
5. Figure out of you want to write for mass consumption or your own niche audience.
These are the two paths you NEED to figure out before you start. If you pick mass consumption, you'll have an easier time getting published and will likely have a more consistent income from it, but your work won't be that interesting so it won't be in the public consciousness for long. It'll be another isekai in a sea of isekai, essentially.
The other option is to produce a story that suits your own tastes and genres. These are notoriously difficult to publish because Publishers are risk adverse. Most people who want to do this usually end up self-publishing. Be very aware that there are people who vehemently think Self-Published is some kind of dirty word and it's not. I've known self-published people making very successful careers making stories that would never get published by a traditional publisher. One such story back in the day was "Fat Vampire" which is exactly what you think it is, a comedy about a newly turned, obese vampire. The authors made a sizable chunk of their livings off those books, the other chunks came from other self-published books.
6. Temper your expectations.
Author pay is, for the most part, garbage. If you're going the traditional publishing route, you're gonna usually get paid in a large lump sum and told that you won't get another paycheck for that book unless it makes more money than what they gave you. Most books published will never do this and so you'll have to make ANOTHER book just to make sure you don't starve, and then another and another until you've made such a backlog of stories that people will seek out your stories specifically and drip feed that debt.
If you're self-publishing then whatever publisher you go with is going to chunk into your income and you'll only get a couple dollars per book. So the same strategy used by traditional publishers is also gonna be used by the self-publishers. It's a tough road for both of them. Also don't forget that there WILL be people who buy your story...and never read it.
7. Be very wary of who you work with.
Publishers, both traditional and self-published, can often have some VERY shady contracts. Some locking you out of even touching the rights to your stuff, even after they told you it would revert back to you. Trust no one, get every financial agreement in writing before signing up, read everything and be very careful on what they ask of you.
Here's a trick shady publishers like to employ. They ask in the contract for digital rights to your book. The problem? "Digital rights" is a huge umbrella and they're saying "Let us do whatever we want with your stuff when it comes to the internet" and asking to get away with it. Did you want a cut of the Audio Book money they made using your story? Tough luck, champ. "Digital rights" needs to be specified. "Digital Right to english release in the United States on X website" is the kind of specificity you make them tell you because if you give an inch they will take a planet.
Welp that's enough of my ramblings today.