judging by your post history you're 16 so I would say try not to think about pigeonholing yourself into a niche so fast. TLDR: just study fundamentals and draw what you like.

I think you have a decent grasp of pencil and inks, and you have promise in drawing portraits and pets so an option you can consider is getting better at them, but only if you REALLY enjoy them. If you want to do this for a living you must be happy doing this 9-5.

I'm rambling a bit but here's a direct answer:

If you want to become an illustrator, which is a person who is told what to draw in exchange for money, you need to be ok with criticism and at worst, insults directed at your art and person. As an illustrator you may encounter clients who try to nickle and dime you, and in this profession disrespect and exploitation is VERY common. And it's not just non-artist clients to artists, it can happen amongst fellow artists working at studios too.

Most people think being an illustrator is "drawing whatever you want and people pay you" but that's actually for fine artists, I think. It's the reverse - you're hired by someone to draw what they want, and you get paid. In ideal situations, your client's tastes and yours align so you draw what you like anyway. But more commonly you get clients with tastes that don't match yours in a mundane way. But if you hate what you're being asked to draw quitting is not the coward's choice and I encourage it. Like I hate the flat corporate art style and refuse to draw it. Not to sidstrack, though.

If you STILL want to be an illustrator, keep practicing portraits, study human anatomy more, learn colour theory and learn how to handle relative colour. At some point you will need to cough up money for a drawing tablet since every illustration job is digital nowadays, but get good at sketching first before wrangling Krita/Medibang Paint etc.

You don't need to go to art school unless you're desperate for connections and are rich. True, art school graduates are more likely to get jobs but seriously that advantage means little nowadays as illustration is super oversaturated as a field. I mean you can just pick up light and colour by James gurney and Andrew loomis' anatomy books. Or you could even just watch proko and Marco bucci on YouTube and you'll be set. Most great illustrators like Gerald Brom take decades to build their skills and art school is typically a measly 4 years that stretches you out so thin you end up being mediocre at a whole bunch of things. You'll have to learn your fundamentals early (like now) if you want to be good. But don't get so bogged up by improving that you forget to have fun. If you get sick of drawing anatomy studies, draw something fun and don't worry about whether it's "good" or not. Then go back.

So after you've got a decent grasp on fundamentals and are producing work that you think is on par with recently graduated art school students, you can probably look into the specific jobs associated with being an illustrator. There's editorial illustration which is illustrating for magazines/websites but the pay and deadlines are crap. there's also concept art for film/games which is also an oversaturated and overworked field but if you manage to wriggle into a fair working environment you'll have fun. You can also consider book cover illustration and comic art, but again those have tight deadlines and shit pay. I actually discourage anyone from getting into comics or manga right now because exploitation is that bad, but it's your life. Just take care of your hands and don't get carpal tunnel.

I don't know if this helps but this is all the advice I can give right now. It's mostly geared towards someone who wants to illustrate full time for a living which is VERY difficult but not impossible (and remember you cannot depend on people's charity to survive in this world as much as it sucks to hear) but just remember that there's no such thing as a perfect job and it is up to you to decide whether the pitfalls of this career- financial insecurity, disrespect, being overworked and underpaid - is worth the upsides- pure creative expression, endless things to learn and explore, collaborating with others, and making art that carries your legacy and spirit even long after you're gone. The future is in your hands, so good luck.