I this is an odd question to ask but hear me out. I notice today's manga artists are very precise with their style, with anatomy, consistence, details and line work. Which is not a bad thing mind you, but I also notice most manga artist's styles are very safe; they know how to draw but are very afraid to make any errors.
This is why I'm looking for manga series with amateur type of art styles. I'm not saying being an "amateur" is a bad thing but I do notice most amateur artists tend to be more creative and grow in different ways.

Examples of amateur art styles are series like Nichijou, Shingeki no Kyojin, and Zombie Powder. The art styles aren't bad at all, but you can see a lot errors on the anatomy, small details, the poses, consistences, and the own style itself just by the first chapter alone. The art styles are off but personally they so a lot personality. I feel like the artist is not afraid to make any errors and learn from them.

Reason I'm asking for this request because just by looking at these art styles kinda give me some hope. Hey, I draw a lot and I always feel like I'm not improving, I always feel like the only way to make it to the top I need a top notch art style. But by looking at those series I shown, maybe starting at the bottom isn't a bad thing.

________________

Yo no Na wa Zushio - this is not only ametur, you can even consider its 'bad'. however, the story is just too hilarious, and i think the bad artstyle just make it even more so.

angel densetsu - this is the classic evolving artstyle. you can see the first three volume the art is not that good, the panelling is static and the actions kinda stilted. but the artstyle improve considerably after three volumes, being very pretty.

Onepunch-Man (ONE) - this is very bad, and more of a draft, but the story is seriously funny you dont really care

Mob Psycho 100 - this is another manga from ONE, more polished but still not very proportionate artstyle. the characters and comedy just save everything.

Some possibilities -

Angel Densetsu seconded - Shounen
Fukuyadou Honpo - Josei
Hana Yori Dango - Shoujo. There's a massive change in art style just over the course of this work
Dokuhebi-san ni Gochuui o - A shoujo oneshot that particularly struck me for having artistic flaws. I wouldn't recommend it for any other reason though, it has a dull plot and characters and so on.

Have you read Bakuman? It's not newbie art, but you may find the story inspirational.

Black Haze

________________
Favorite Manga | Yotsubato! | Hinamatsuri | Barakamon | Hayachine! | Itsuya-san

I would say Chronicles of the Grim peddler. But while i'm not sure if it's exactly "amateur" I do notice there is a lot of disproportions going on with the art style, such as people having hands as big as their heads or ridiculously long limbs.

Ares, almost didn't read it because of the art, but I'm glad I did. Amazing story that makes you forget about the uncommon art.

Bring this page back up again.
I still want more amateur manga art style.

________________