I'll give my reasons before people beat me to death.
My Opinion: Legit, I've seen worse fanart. I think this is probably one of your few times you ever drew an anime girl, so I understand why it doesn't look the best. It's still, not bad what so ever. I'd give it a pass, though giving some advice before it's ever showcased.
1. The head and neck are somewhat wonky. The chin is more circular as you gave the girl a BIG neck. If you meant to draw it close up, makes sense. Though you drew a full body pose. Measure the amount of limbs and body parts before getting to the finish line.
2. Again, measuring body parts before continuing. The hands are actually something I suck at, so your hands look nice! But because the arms are shorter than the neck, it looks like she's either physically wonky or she's looking up. If you plan to position her looking up, move the chin up and flatten out the shoulders.
3. There is no nose or ears. That is all. Just ,, try and add one, even if it's a literal dot or if your character doesn't even have ears.
4. The eyes are HUUGGE, and I understand some professional animes use this technique, but if you want to go for a more professional style, measure the placement of eyelids, pupils, and other stuff via face and cheek line. That way, she looks like a girl and not a doll.
5. I honestly have no words for the boobs, cause I cannot draw good boobs at all.
6. The color composition is simple, which can be a very good thing. I like how each color blends properly, but there's no shading, highlighting, nor contrast. It also looks rushed, so practice lighting with colors, going from lightest to darkest. Do this for hair, pupils, skin, and clothes.
7. The speech bubble is your own choice of style, and I don't hate it. I just want to tip you that if you want people to see what your character says, make the speech a tad bit bigger. Otherwise, it's fine.
8. The hair is decent, but you sure you wanna give it that position? The more bouncy, the more fleshed out your character is- including colors. Go for light brown, then lightly press the brown crayon/colored pencil, then darken, etc.
9. If you wanted cartoon-y eyes, this is fine. Otherwise, Try composition experiments with pupils. Doesn't matter what color- it'll be fine!
10. She looks so stiff.. this is fine, however the more you practice body positions, the more HUMAN they look.
