UPDATE: I wouldn't take these suggestions very seriously anymore, I'm not really learning much ever since i started working full time. Being an adult kinda sucks sometimes
Will edit it as I read and learn more. That being said, I'm just starting, you can see my crappy anime drawings on the drawing thread.
Bert Dodson - Keys to Drawing: Really good book if you don't know how to start. It teaches a little bit of everything and gives you exercises as you go. It's available on the Internet Archive but you can probably buy a physical copy for a good price if you prefer.
Ernest R. Norling - Perspective Made Easy: Title says it all. Perspective explained in a tremendously easy and simple way from scratch. That being said, my impression may differ since I did tons of perspective in school back in the day. Also available on the Internet Archive and easy to buy physically.
Andrew Loomis - Figure Drawing for All It's Worth: Probably one of the most famous figure drawing books. I've seen it recommended a lot by western and eastern artists alike. It's on the Internet Archive too. Physical book price seems a bit higher than the previous two, but I haven't looked much (only found hard cover) and it's still a reasonable price.
Jack Hamm - Drawing the Head and Figure: I have seen more eastern people talking about this book than the previous one, but I am not sure if there's a 'better' book, and I guess I can read both anyways. It's available on the Internet Archive on loan, so I'd suggest you to find pdfs elsewhere (they aren't that hard to find). It seems like the physical book is cheap and easily available anyways.
Drawabox: This was the second place I used to study fundamentals. It tries to teach the construction method from zero by using text, videos and exercises. The result is a program that starts focusing on the small stuff and works from there. The teacher of this course made the course after having taken the Peter Han's Dynamic Sketching course so they have some similarities. The opinion of this course is very polarizing and I ended up dropping it halfway through lesson 2 and after finishing lesson 1 and the 250 box challenge because I didn't really see the point anymore. I still learned some things from it, it was more like, after what I did, I checked the latter exercises and I didn't think I could benefit from them. Drawabox is free, but, even though I haven't personally done it, I'd recommend people to do the Peter Han's Dynamic Sketching course if they manage to, you know, get it for free somewhere like on a four clover leaf website. Otherwise, Drawabox's first 2 lessons (and probably doing 100 boxes instead of 250) are not a bad option.
Pixiv Sensei: Jap only, but I started here and it helped me somehow. Just gives you simple methods to do simple drawings and skips some stuff that I think would make it easier. Still not a bad option to loose up and have some fun, just something I wouldn't expect much from.
Vlippu's figure drawing course, Brent Eviston's figure drawing course...: I really don't know much about them, only have seen people talking about them and they seem decent. I only wrote them if anyone wants something to start with. They are not free, but I guess you can find them a certain four clover leaf website too...
Naoki Saito illust Channel: Illustrator of some Pokemon Trading Card Game and Duel Masters Trading Card Game cards, main character designer of the mobile game Dragalia Lost, and author of Baki Domoe, a comedic spinoff of the Baki the Grappler manga, he also has english subtitles on plenty of his videos. Even if you don't plan to learn how to draw, his videos are interesting to watch sometimes.
BoichibeTOON: Known for Dr. Stone and Sun-Ken Rock, he uploads videos with TTS on English. I think it's interesting to see the point of view of an actual manga artist on certain topics.
Drawing is hard as fuck, you will draw 200 times something and still be dogshit somehow. It is important to learn the fundamentals from sources like the ones I've mentioned, but also to draw dumb stuff and enjoy yourself every once in a while or you'll end up tired of everything.
People usually recommend to just copy the drawings of artists you like and make studies, but I think that watching one or two youtube videos about how to draw the head and figure (or Pixiv Sensei) could help you to loose up a bit and then start to copy and have fun. I started with Pixiv Sensei when I began to draw and spent a year doing random drawings before Drawabox. I don't think that anyone should follow on my example (that year was too much) but it's true that I could confront the fundamentals with a bigger motivation as I saw myself stuck and I wanted to improve after having fun drawing.
Also, as a general recommendation, I wouldn't recommend you to start straight up with figure drawing anyways. I think resources like Keys to Drawing (or even Sensei) would be a better place to start.
Joining a community and see other people talking about art is exciting for me, but sadly the only place on the internet is /ic/ and some random Discord servers. /ic/ still has some resources and I've seen myself looking on archives for thoughts of people about certain things so I'd say there are some decent people on there.
As you start to progress, you start to understand how big of a gap there is between good artists and decent artists (at least when it regards to twitter anime artists) and how even decent artists are so much better that you'd think after looking at their drawings and comparing them with yours.
As for me, I want to draw a oneshot one day, but I don't really have my hopes on it. I don't intend to make an art account as I am not interested on comissions so it'd seem like more of a liability that something funny and, to be honest, the people who I really want to show my drawings would check the Drawing Thread anyways.
Finally, in case is wondering, the order in which I've studied these things is as follows. I don't really think this is the only order in which you should follow things though:
Sensei -> Drawabox -> Keys to Drawing -> Perspective Made Easy