I think we kind of lost the topic here and got totally side-tracked with a conversation about fanfic.
I haven't done a lot of marketing recently, but I used to do my best with it. Granted, it was on wattpad, so advice might not work out quite the same here.
A social media presence is very helpful. Appearing to be an interesting person will get people to check out your work. I gained several dozen followers from twitter and tumblr when I was active.
Being active in forums/whatever the best option here to make friends with other writers is also big. Check out other people's work, leave some helpful comments- a lot of times people reciprocate. I've seen threads here that do it the organized way with a sort of critique for critique system like they did on wattpad. Making friends also gives you both the chance to put spotlights on each other's work and share your followers especially if you're in the same genre.
I've found in my years that webnovels have a very strong social aspect when it comes to marketing, unlike traditional novels.
Also, since we're talking about fanfic, that's also a good way to grow your audience. Fandoms are huge, and fanfic grows in popularity by the second, lol. You pull on a huge audience and you can catch dedicated readers for your original novels from that pool of readers. Whether people approve of it being allowed on Tapas or not (I don't, tbh, all my fanfic goes on AO3) it's still a good way to pull in readers and get them interested in your writing before advertising your original works.
Fanfic often falls under the terms of fair use laws, so as long as the fanfic is transformative enough it wouldn't violate usage terms because there is no copyrighted material being used (except in any images, of course).
Of course there have been bloodthirsty lawyers who have gone after fanfic in the past (god, I remember that fear, and the poor people who got snagged by some very high profile author's lawyers) but technically fanfic is okay so long as they're not copy/pasting and are relatively original in plot and such.
The only thing you'd have to worry about is earning money from it (ads and tips) because that's where problems usually occur.