I'll stay in this post because twitter is difficult
I'll second @Lirina's suggestions. I've had a lot of fun and better success getting into groups of people who like similar things. Use relevant hashtags, interact with people, participate in twitter events, retweet folks, and you'll find your people.
Unfollow, mute, and block are your best friends, don't be afraid to use them. Also, don't feel pressured to follow someone back if you're not interested in what they post, or your feed will be full of stuff you don't care about and you'll never see the stuff posted by people you like.
Twitter doesn't have a chronological timeline feed, so you'll have to fight their algorithm to get seen. The algorithm on twitter rewards frequent posting, and your audience will more likely see your posts around certain hours, so if you care about that kind of thing, setup a Buffer or Later account and schedule your posts for prime hours. My audience's prime hours are around 2pm, for example. Contrary to popular belief, the algorithm suppresses posts with links and hashtags, so use them sparingly.
Twitter rewards constant use, like several tweets a day, and appealing to trending topics. Fanart gets WAY more engagement than original art, even for artists who are quite up there. The conversion rate (how much people are willing to click links you share) is lower on Twitter than almost any other social network, so if you're looking to grow an audience, it's a bad place to go. You need to already have an audience when you start Twitter, for the most part.
If you're just going to be social, then it's definitely not where I would go (way too cynical and negative), but if your friends are there it might be fine.
Since when is it common courtesy to follow people back on Twitter? That's never been a thing among any of the artist circles I run in there. We follow people because we want to see their stuff on our feed, not because we feel somehow obligated.
Follow for follow is a bad idea anyway, all it creates is massive feeds full of stuff nobody wants to browse through and see, and inactive followers messing up the algorithm which determines how your stuff is ranked and who sees it. (Which can make or break a post.)
As for how to use Twitter, you rely a lot more on occasional bursts of 'virality' to grow. Those are pretty rare, but they can happen. Other than that, here are my tips:
- Join in on art shares maybe once a week. (Don't overdo it, or you'll put off your current followers.)
- Comment and engage with other people's work. That can get eyes on your avatar, which can draw people to check out your account.
- If you're posting stuff about your comic, @ Tapastry_TCC and @ WEBTOONCanvas whenever you do. Sometimes they'll retweet, and you can pick up a few followers that way.
- Block anything you find drains your mental or emotional energy. Twitter is a hellish place if you stumble into the wrong sides of it. Thankfully, you can block keywords, hashtags, and people. I block anything remotely political, it's a horrible place for such discussions.
Twitter is still kind of fresh to me. Over the years I've kinda ignored it and just had my username parked in case I ever really figured it out. I had a couple comics go semi-viral after I started just sharing the same posts I share on Instagram so I started just keeping that up. The work I post on social though is specifically made to be a little more grabby and sharable so I hit like +15k more followers after really leaning into it for a couple weeks. Now I just keep doing that and occasionally using it for more casual chit-chatty tweets. I more or less treat it the same as I do everything else.
I don't think that's really the approach for everyone but it definitely worked for me! 
It's what the courses about Twitter I did told me and I've been seeing it in praxis on my blog's Twitter. Maybe it's different for artists who mainly use personal accounts but it's what professional accounts do
I wish I could help but I tried most recommended tactics and so far nothing worked for me. 
I just can't post everyday as I pretty much only post art, I don't like to post about my personal life on main (which apparently is seen as a bad thing on twitter?).
My posts in art shares always flop, even if I manage to post within the first half-hour of it, before the thread is flooded. I think the only thing that worked a little is commenting on people's posts, but even so, a follow back is not guaranteed, they might not care about your stuff or not have time to check it. It's just how it is.
It does though! (On desktop for sure, haven't used the app in like a year so I'm not sure about it) But the average user is probably unaware of this, the "top tweets" feed setting is default and obnoxiously turns itself back on after like 3 days max.
There's also Tweetdeck (always chronological) which, combined with Better Tweetdeck addon is the least annoying way to use twitter and it's what I do.
hm.... it can be good to expand your audience BUT people there tend to be a bit harsh (i use it but for personal use not for my novels) and i see people hating on pretty much everything 
I follow dozens of professional artists, including professional comic and webcomic artists, and it's definitely not a thing in that field. Maybe it's different among writers and bloggers, but I can 100% confirm if you follow a popular artist expecting a follow back, you'll leave disappointed.
I know nothing about writers Twitter, though.
Oh, which - back to the topic of the thread - is another tip for Twitter! There are distinct subgroups within Twitter, which have different norms and expectations. Art Twitter behaves differently to politics Twitter, which behaves differently to fandom Twitter, which behaves differently to science Twitter... and so-on. So it's a good idea to pay attention to those norms.
Of course, top artists can't follow everyone back. It's more a numbers game: if you follow 200 people and maybe 100 will follow back. I learned it in a course that wasn't specific to any niche but I guess it does work more in some than in others.
My main Twitter is in the personal finance niche where it did help though to be honest, I'm also not a fan of this strategy beyond gaining the first initial followers for a new account because it doesn't help with engagement at all
Aaaah, yeah, I've heard that advice, I know where you're coming from now. (Though I'd heard it for Instagram.) A lot of new accounts will follow hundreds of people, then unfollow a week or so later, rinse and repeat. I remember once having the same account follow and unfollow me three times.
No, professional accounts do not follow-for-follow. At all. I say that as both a writer and an artist who follows many of the professionals on Twitter. I've been part of a massive campaign involving the entertainment industry that lasted over 3 years. Being followed back by professionals, even if they like your posts and agree with your movement, is a big achievement. I don't know what course you took but please, listen to actual users here. Follow-for-follow is never required and shouldn't be taken lightly. That's how you get hackers in your DMs.
First thing I'll say upfront is: RUN! lol I'm not really kidding, though. Twitter is just about the most toxic social media there is. Okay, maybe Facebook but they tie for first.
Secondly, no, you are not expected to follow-for-follow. In fact, anyone who has spent just 3 months on Twitter will tell you that's a dangerous idea. You'll get a lot -- and I mean A LOT -- of scammers, spammers, and hackers following you so that you'll follow them back. This enables them to send you direct messages (DM) with virus links and hack your account. It's pretty common on Twitter if you get into the habit of following everyone and allowing personal messages.
Professionals will very seldom follow you back. Take a look at their follow vs following lists. They could have 100K followers and only follow 4 people. I suppose some will follow a lot of people, but again, don't go into it expecting you to be one of their chosen. They value their privacy and don't want thousands of random users' content showing up on their feed.
Honestly, though, Twitter is just .. toxic. Even the professional artists and writers will show you their rude, uncivilized side on Twitter. I don't know what it is about that place. I've been on it since 2011. I went away for a while because I was so tired of the drama. Went back for an entertainment campaign and it's only gotten worse.
If you really want to join Twitter and you're doing it to promote your work, avoid religion and politics at all cost. In fact, just anything controversial. That's just an invitation to get bullied, harassed, and have gladiator-level fighting in your comment section.
.... Why am I still on Twitter again? 🤦🏻♀️
My biggest advice right now is to find an extension to block things like Twitter Trends, Topics to Follow, and the like. The ads are a bit harder to work with, but blocking the others will make it easier to shape your experience. A lot of Twitter Trends do deal with politics, news from your region, random hit tweets, and other trending things you may or may not be interested in. I currently use the following link for Google Chrome (I don't know if there are extensions for other browsers, but there should be):
After that, think about following the webcomic sites you're posting to. Webtoon Canvas and Tapas Tapastry are currently on both Twitter and Instagram.I use both as a way to not only promote my work, but also promote the work of others, keep up to date with events, and see if they have any activities going on.
Also follow artists you've been keeping up with -- take note on what they post and how they interact with their audience. You don't have to mimic them exactly, but understanding their process can add more to your own.
I also find that a lot of people enjoy WIPs. Posing process gifs, sketches, and the like, along with questions or your thought process, can really get people engaged with your work.
Another good thing to do is use hashtags. But use them related to your brand, along with broader ones. You want to not only target a wider audience, but also the people you're targeting with your story.
Example hashtags can be:
ArtistsonTwitter
Webcomics
[Whichever genre your comic is: Horror, Comedy, etc]
{The niches/tropes within your comic: Monsters, Demons, Isekai, Princesses, Robots, etc.]
Webtoon and Tapas also have their own hashtags they use, which can make it easier for staff to see your work.
Even more -- engage with other people's works. Like likes, retweets and comments and even think about promoting the comics you enjoy. The biggest help you can do for your own work is promoting others and showing audiences that these things ARE popular. That people DO like them.
Oh yeah, it's been a while since I've actively used twitter and I completely forgot about tweetdeck! That version of twitter is so much better than real twitter in every conceivable way
Somehow my Twitter is more successful than any other platform. I can't necessarily say this list is a guarantee for success, but here's what I do on there:
Start conversations about webcomics (i.e. "Hey webcomic creators, what is your process for _______") It encourages other creators to reply, which in turn boosts your tweet and helps it be seen by others. Likewise, respond to other people who post conversations! Art shares can also be good too, but those seemed to create better engagement a couple years ago.
When I write tweets, I don't use hashtags, but I do include buzzwords relevant to what I do! I try to include the word webcomic in all of my tweets (i.e. "My webcomic Future Agents updates today," "I love webcomics because ______.") If anybody searches for webcomics on Twitter and they choose the latest tab, then my tweets will pop up. (I use this to find webcomic artists on Twitter!)
Support others by commenting and retweeting their posts (But be genuine!)
Experiment with the time you post and then try to post consistently around the time that draws you more engagement. I tend to get more interaction in the evening (6:00PM CST - 9:00PM CST for me) It takes a lot of experimentation to see what works for you.
It's okay to repost your artwork because new people will always see it. Quote tweet old art posts, bump them with comments, retweet them, etc. Tweets seem to have a limited shelf life and self-boosting can help extend it! When I post at night, I usually bump my Tweet the next morning by leaving a comment under the original Tweet. It always seems to get more people to see it.
If you have mutuals who interact with you regularly, hold onto them for dear life. The webcomic community is pretty friendly on Twitter and we love to support one another!
Twitter can be fairly exhausting, so I try to limit how much I scroll through. I make lists of my favorite artists that I can go to so I make sure I don't miss any of their art. I tend to turn off retweets from anybody who shares non-art related things so my feed doesn't get clogged up. And I don't explore trending topics because they almost always derail into a toxic environment. Blocking is your best friend! I block all sorts of ads and unsavory profiles.
Damn I wish there was an extension like this for Firefox 
Even tho I mostly use tweetdeck, occasionally I have to use the main site and these always hurt my brain.
I set my trends location to Japan (and I'm not good at reading Japanese lmao) just so they don't distract me as much, but it doesn't work on both my accounts and occasionally returns to my default location, for some reason...
But what if your WIPs get more engagement than the actual art I stopped posting WIPs on main because of this. (Though I guess, some way around this is to post the WIP/process gif after the actual work, in a start-to-finish fashion.)