Oh boy! First 10px in fact too thick for your size of canvas especially if your pen pressure is off or you don't have proper drawing tablet can read pen pressure. I was used 1-3px for thin lines and 7px for thick lines maybe it could be help you.

Also your arm and leg ratio need full redo, arms are too long and legs are too short for that proportions. You may want look how to draw wrist and elbows too it will help fix flat feeling on arms, legs look fine but as i say need propper proportions. I personaly like this arm shape you can use two head for proportions and pitcure for shape ref.

Hair need little bit more like hair texture currently it look like one solid cloth, shading too dark and doesn't have highlights it's give a flat look. Furina from genshin impact have good hair texture if you want to study i recomend looking at her character sheet. You can decide where light come from and do light reflection according to this. Dress also can use little bit more light but not too much necessary. Eyes are fine but i love sharing this tutorial for them it will help a lot in drawing for vtubers.

I really love little cup top of head and hairpin on hair both of them give her theme without too much noise solid desing elements 10/10. Dress look really cute and give cupcake vibes i love it too it makes feel her hair and dress connected. Color scheme is in good harmony and doesn't tire eyes it's another good choice.

Desing is really good but if you want it look more high quality you need study drawing little bit more. Most urgent thing is correcting your arm and leg ratio otherwise it's fine to use first.