This an interesting thread.
What I've seen, above everything else, is to do more research on how each of the platforms work and how to advertise, because they're all different, I'll share the ones I've been using.
But despite that even professionals in whatever they do will say this and I will agree: don't stop keep consistency and keep posting, it's not that your product is bad, but rather it's not good "yet" (in terms of story). Leaving things to luck is the same to leaving the wheel to Jesus, it's not a thing and it doesn't work lol.
Devianart.
In this place sharing in groups is what has been helping me the most, like a FUCK ton of groups, I myself have not had any bad experiences, most of those have come from tumblr for me personally. Also since I have gotten my art to a level that bigger groups will accept me now, and those gain a bit more traction, but I don't stop there, I go share in more groups than it's needed but it helps because it catches people's eyes.
Instagram.
I personally do not like using Instagram for advertisement mostly because I can only use thumbnails and not the actual comics, but due to facebooks policies (in regards to image use inside of the platform, because insta is also part of it) I do not trust posting my comics there. I just hate the image format and I don't have a good cellphone to use is as intended. But even posting a thumbnail of an update helps.
Facebook.
A lot of people don't use this anymore, but a lot of people still do, and there is still some gain from it, mostly from sharing in art groups and comic groups, and this is what has given me more traction to Webtoon (specially) and Tapas, it's just a good way to get your comic Advertised. not so much for posting the comic, unless it's a funny short strip, then it's gonna get a fuck ton of notes, people love those on Facebook and that's their specialty, for a longer format story, then just advertise.
Tumblr.
is very dead..... I barely get notes or anything!
I have 1000+ followers and get like 3 notes.
Only times I get more traffic is with fanarts... and it's not a lot anymore.
Edit on Tumblr:you have to speak a little bit more on tumblr and people seem to notice you lol, sometimes asking questions will get people moving lmao. iff something more happens I'll tell you.
Twitter
I think it's more of a matter to find which bot blogs auto-retweet and consistency, I haven't grown to fast there yet but I've seen a trickle everyonce in a while. it's a matter of who to tag (@ someone) and which tags to use so bot blogs find you.
Artstation.
An odd one, but I've seen a particular artist post a "comic" more like a series of images with no text, I've forgotten the name, it's the most professional place, but people read it and it gives you a ego boost if you see like a pro artist liking your stuff while you loose your shit hahahah. But it's very hard to gain followers, since that place is for industry professionals or people seeking a job. I'd suggest, make your are good if you even consider posting there.
Newgrounds
Worst place for a comic, but I still put it there, because you can still re-direct people and if you can catch people's eye with your artwork is a guaranteed follower, that being said Newgrounds culture is different because criticism is encouraged, so if you don't like that, don't go there, I'm okay with it because I already know what I'm doing. It's a bit of a grind to gain followers as well but there is a community that does like to help :3 If you have questions, they'll most definitely anwser, but if you gotta post a comic, PLEASE LEAVE LINKS, BECAUSE READING ON NEWGROUNDS IS ATROCIOUS.
Furaffinity
If you don't have anthorpomorphic animals it's a super weird choice, I've beem there because they help with commissions, but at the end of the day I use my gallery as I use all my gallerys, with very few furries lol (unless you have open requests, then expect a flood lol) but people have actually posted comics and it's not a bad reading experience there, now it doesn't mean you cannot put a comic if it absolutely doesn't have furries, because if it looks interesting, I've seen that they will want to watch, they're superfriendly, so there is a bonus there lol. I've been getting more followers conssitently so I cannot complain much.
Reddit.
Kinda like facebook is a good place to get your comic advertised, it's more about consistency and how many groups you can find to do so, I have very little experienve with it, so those are my observations so far.
Minds.
It started with politics, but I've noticed more artists coming there since twitter has been pushing people for a lot of wrong reasons, I've also seen Japanese artist mention it as a replacement for twitter, and it works similarly, but you can only post one picture per post, and only use 5 tags, it's a weird combination of facebook and twitter, and it doesn't have too many artists, so getting traction, is super slow, but artists are starting to arrive more and hopefully it gets good for art. I'm just there to see what happens and if it grows more.
That's it :D!