My target demographic would be generous adults with monies.
But it seems like my stories attract teenagers 
Next time I will make my story more complicated, I guess.
To tell you the truth: I rarely think about what my target audience are when I create my story.
I make the story the way I want, however I do try to make my story more simple & universal to draw in readers. The story has teenage protagonist and it's a lot like shounen manga, but tells in a art-house movie kind of way. It's not pulpy that's for sure and I hope my readers realize that.
My comic does not contain clear romance so it doesn't limit out readers who only like straight romance or BL etc. Also doesn't have very strong sense of male/female gaze (except some comical characters) Also I don't want to focus on character representations, just be story oriented. (aha this may limited out some readers too)
I do try to be as approachable to most readers as possible but in the context that they have to be able to stomach my anthro designs & the story (and also my not so good English, which could be a welcoming thing for international readers 
) Also when future chapters where things go dark, I may lose some readers too. that's understandable and I'll be okay with it.
Most of all one just have to show off the uniqueness of your work (within rules), and do so confidently. There will be audience who like your stuff.
I think the main thing is that you now understand trying to make something for everyone is really tough and while not impossible to do solo, probably requires an entire team of people.
That said, I personally believe that the notion of picking a set demographic for your work is something that matters only if you're set on marketing it and/or selling it to a big publisher. Because in that case, the stats and details really matter.
BUT
If you're only interested in making a comic for yourself and you're not hanging any monetary expectations on it, go for broke and make the comic of your dreams.
In that case write the story you really want to tell and let it find its own audience over time.
Edit:
I just realized that I didn't say how I chose my demographic for Dragon Sparking. I basically make what I liked to read when I was 12-13. So pretty much Middle Grade Action. Even though in actuality, I don't have any stats on the ages that read my comic
I sort of keep my series in the PG-13 range. I am not really interested in writing 18+ stuff. I do have one series which is All Ages and I guess the struggle is making sure you write something that no one would find offensive but a kid would still enjoy reading.
My series Sugar Land was also suppose to be All Ages but I one point I just gave up. I heard someone set out a challenge to comic creators to create more LGBT stories that preteens could read without having to deal with adult jokes. That is what I originally set out to do for that series but I definitely failed.
@DokiDokiTsuna @allenT @nathanKmcwilliams
Thanks guys. So basically what you're saying is "If you build it, they will come?" Do you think it might be a good idea to write down what I think I would want to write and see what comes out? Would that be a good exercise perhaps?
That's the theory yeah. But there's still plenty of other factors into getting eyes on your work, just making it isn't a guarantee.
But the real question is do you even want to get back in the game yet? Or do you still need some time to process and relax?
Whether or not writing down ideas is a good exercise depends on you, really. For me, I already know what I want to write, putting it down on paper doesn't help me at all.
The thing is; i'm not entirely sure. I've made a lot of progress in general over the past few years and especially recently regarding a lot of stuff and just in general have been really unsatisfied with the fact that my life's been more or less "On pause" ever since I got out of high school due to a variety of factors and I just feel the need to do something to channel that energy and occupy that time if that makes sense. Whether or not that means finally pulling the trigger on a long form fantasy comic, finally getting a job, or finally finding a good college, or something else entirely..... I'm not necessarily sure and I'm still trying to find that out.
Might at least give that writing exercise a shot though, sometimes writing/drawing things down to get it out of my head can help me more.
Then, whatever project you do, do it for yourself, on your own terms. Make this your space and your time.
If you saw my comic that is based on the Fantasy genre called Mukhtar, you would think I am targeting some specific audience but nope. I made that comic out of passion. I even planning to make another passionate comic in the Sci-fi genre. I never have any target audience, it's for everyone to read and it is up to them whether they liked it or not.
The target audience is ME
Okay but fr I rarely think about target audiences when I write-- I write what I would enjoy reading or find interesting. I guess in that case my target audience ended up being people who find the same or similar things things interesting: psychological horror, darker stories and villains with complicated relationships with the heroes.
For me it way relatively easy I guess, since my stories have pretty clear inspirations in the sense that I can clearly identify 'oh, I want to make something with XYZ vibes'. So my target audience would be the same as the target audience of my inspirations 
One thing though is I don't think it's useful to think of target audience in terms of age/gender etc. Rather, think genres and special interests. If someone posted a panel of your comic onto a subreddit, what community is it most likely to be?
Don't forget you yourself are also part of a demographic. What communities do you frequent? What tropes/inside jokes are they familiar with? You probably have a few insider perspectives already; tap into that!
I'm kind of bad at aiming for a specific sort of audience. There are a few things I've been trying recently to really narrow things down because I would like to pitch some stuff at some point, and I also of course work for a company that makes edutainment for kids, so I've had to learn to deliberately write for different age groups.
Look up research on what different audiences react to. One of the things we get at work are all these research presentations and things about what colours age groups react to, how they play, how and when they read and watch, how they identify with characters, how many things they're a fan of, their vocabulary level etc. Actually a really good resource when writing for kids is to look up the school curriculum or syllabus for that age group to find out what the base level expectation of knowledge and vocabulary is for them.
Comp titles. A comp title (comparison title) is a series you can point to and say "it's kinda like this" when pitching to publishers. A comp title should be in the same medium and aimed at the same audience as the thing you want to make (so a mistake I made on Errant was I went in with Netflix She-Ra and Steven Universe as comp titles even though they're animated and webcomics are a different medium with different demographics and trends), they need to be within the last 10 years, and they need to have done pretty well (A publisher isn't going to be put at ease if you say "it's like this comic that was a total flop."). So if I wanted to pitch Errant as a Tapas Original now, I'd have Pandora's Devils and Hard Lacquer as my comp titles (because most people who subscribe to Errant have them in their libraries and they're both popular Tapas Originals), and for a print comic I'm planning that's for kids, I have things like Witch Boy and Amulet: The Stonekeeper. A good start is asking friends for recommendations, seeing what people who follow your work are into and just reading a bunch of comics and being like "Aha! This one is my vibe!"
25 days later
Like @smokesalty wrote,
my target audience is usually me.
But that depends on what I want to achieve, I´m taking part in a comic contest right now,
the comic will be printed when we win and be eventually read by kids, that means the target
audience can´t be me anymore and I will make it kid friendly
My target audience is pretty niche. (Anyone who likes sci-fi horror with industrial themes, body horror, etc. and also like manga art.) I didn't really have a set plan but I just post my work and follow similar creators. It's helped build an audience over the years. 
My target demographic would be older teens and young adults who are into Pastel Goth, dark and edgy stuff. My series "Stacy The Demon Killer" is a parody and mix between Buffy the vampire slayer and devil may cry. It gets pretty violent with all the blood,gore, and swearing, so it's definitely not for everyone.
My two series is targeted towards battle shonen and seinan fans, though they're both novels. One I made Crusaded Defender is a series that I hoped HxH Fans would like and Agents of Salvation is a series that I believe would gain the attention of D.gray-man/monster fans so these are not flat out plagiarized carbon copies, there's just inspiration from those series mixed in. I also was targeting an audience who was in late teens/early adults range, both series are action, with Agents being horror and tragedy, and CD being Adventure. In the end I hope that kind of audience is present on this platform.
I honestly don't decide on that, nor even think about it too much.
I'm an artist for hire, so, for the three webcomics that I work for I just apply for the job if the story interests me and the pay is something I can consider a win.
When it comes to my personal projects, I don't have great dreams of making my work noticeable, to be popular or to expect it to be animated in any kind of format. I never thought about that because I have no one else to satisfy besides myself
I'm very simple, I just think: "I want to do something in a certain way because I don't find content like this or that is specific in X aspect / I had this idea stuck in my head and began to make a story around it"
18 days later
Mine is somewhere between 12 (British equivalent of pg-13) and 15 rated, due to the fantasy violence, disturbing topics and occasional gore. I didn't want it to be too childish, but I didn't want to write a hardcore adult story, so I settled on a teen and up audience.
short answer I dont decide the audience, since im writing this story for myself first and formost that came second.
i have however noticed most of the people who read it or the people i show it to and like it a lot are people who identify deeply with what the story is telling readership seems to be 50/50 boys and girls and mostly in their mid- late 20s
A lot of other people tell me the story makes them uncomfortable cause of the subject matter or its good but its not for them.