SHOUJO ARTISTS:
Arina Tanemura - her art is pretty. Have you even seen the details in her drawings? Not A-grade but dang sun so nice. Her stories are meh to me.
Matsuri Hino - again, art is totes amazing. Much better than Tanemura's. Some of her works are good, like MeruPuri and other oneshots. Stay away from Vampire Knight, that series' ending was too fan-biased from what I've heard. Pissed me off even though it's been more more than 5 years ever since I last read it.
Youko Maki - my goddess! Her art is just the beeeeeeeeeeeeeest. Even more than Tanemura's or Matsuri's. It's like rainbows farting, in art style. So nice. Her stories are totally interesting as well though some endings are a bit of downers. I've read most of her works. Aishiteruze Baby is her most known work. Recommend that one. Shouri no Akuma, Yamamoto Zenjirou to Moushimasu, Atashi wa Bambi, Taranta Ranta, etc. She's currently working on two series with her sister, Mochida Aki. One is Zenzen (story by Youko Maki, art by Mochida Aki) and Pika Ichi (vice versa). She has an ongoing series called Romantica Clock, and tbh, her style in this one isn't my cup of tea anymore (her previous art style was more beautiful) so I don't really have an opinion on that one.
Aya Nakahara - You need to stop whatever you're doing and go read Lovely Complex. One of the best shoujo series I've ever watched and read, but mostly read. It's one of those manga that can affect your whole outlook on life, it did for me. But anyways, her art isn't really attractive at first but it's one of those that you get used to once you read more of their work and begins to grow on you. Now, I freaking love her art. Her stories are amazing as well. AH-MAY-ZING. She's put her own twist to shoujo cliches. PLUS. Her jokes in her manga are humorous, it's always the humor that gets me. But anyways, aside from LoveCom, you should try reading Nanaco Robin, Junjou Drop, Benkyou Shinasai!, and basically anything with that name. So nice, humooooooor <3
And I think we all agree that CLAMP is amazing, the goddesses of the shoujo world omg.
JOSEI ARTISTS:
Enjouji Maki - My queen in the josei department. Her guys are hot hot like tater tots dang sun level. Well, for me that is. But anyways, her stories are amazing as well. As expected of josei protagonists, her protagonists tend to not take anybody's carp when given. Well, there are some times when they do but hey, at least they're not like doormat protagonists like some shoujo protagonists ugh. Most of her work has some smut in it but so nicely done A+++ for you Enjouji Maki. Recommended works are mostly everything. Private Prince, Hapi Mari, Atashi wa sore wo gaman dekinai, and her ongoing one, Dear Brother, which I've put on hold cause I don't like cliffhangers. They're the bane of my existence.
I had more josei artists but I'm blanking out right now... I'll probably edit this post once I've remembered them.
, and most of their works have strong female lead! This is a big big plus, as I feel so frustated reading manga with weak female lead. Oh, I like Soon Ki too, she have only 1 work by now though, and I started to like Ishihara Keiko and stalking all her works now. Her art is gorgeous. 
I like it too..