/ic/ - Artwork/Critique

How do I get good enough to draw graphic novels with the level of detail of something like Berserk or Gantz?

I feel like I have several ideas for stories and universes I'd like to create, but they always seem ambitious and far beyond my skill level.

One is of a boy obsessed with adventure (and escapism) in a coming-of-age story, set in a sprawling city with a forested river running through it. There's lots of conjunction between man and nature, old and new architecture, and lots of underground segments.

Another is a fantasy set in a remote kingdom where all the conflict is internal. Lots of castles, monsters, armor and towns, tons of nature scenery.

The last is of a post-apocalyptic future of a crumbling metropolis struggling to maintain itself in a barren wasteland, but there's a reveal of a farce and a brief intermission set in a lush western forest. Lots of hard-edged concrete and steel, futuristic machines and weapons and bizarre creatures.

I'm not a terrible artist but in regards to standards of /ic/ I'm an absolute beginner and couldn't pull off any of the above. I've read the sticky but none of it has helped me with things like how to place characters in a detailed environment with a realistic sense of dimension, and how to draw the same detailed object from several different perspectives.