that's way too broad so you get the general advice:
get some drawing tablet, doesn't really matter which, fire up clip studio paint or krita or whatever and do your best at drawing every day (within reason) for as long as it takes (i.e. years). make and use reference pics, they'll save your ass.
don't skimp out on finishing filling the page/frame. don't shy away from difficult shots or drawing the entire subject. do the whole thing, although you don't need to worry too much about anything but the focal points (faces, eye catching stuff) being especially good.
drawing popular characters can help build numbers up if that's motivating to you. post regularly. beware that effort isn't proportional to numbers, so at some point you'll spend a long time on something that flops. keep going.
>>935 making good are as easy as tracing them; even if you post a render of ecisting stuf or what, doesnt seem you ll get as much traffic either.
individually i rarely see established illustrators flops...it seems genuinely not the case of it.
this isnt exactly legal so i try and do originals, problem is they dont even get as much numbers either.
fanart isn't plagiarism or theft. takedowns are for specific stolen works, and the problem you'll have with selling is with trademarks, not copyright.
this is also utterly not worth caring about for every random work you do. it's not going to be an issue of consequence if you're not bootlegging their products.
established artists do plenty of fanart, and frequently used it to get established. some don't really and that's fine too, it's not like you have to, but it is a way to build up numbers by being discoverable.