Right off you need more contrast between your colors.
Check also the lighting, it's flat and sticks to the edges. Old comparison
here. This also creates banding.
Another comparison (Cure's the man)
You could push the pose there too.
EDIT:
It's a start, it sort of reads.
Yes, keep working on your fundamentals, but also:
Fundamentals might get you 90% of the way there, but there are a few things ofc that don't translate directly INTO pixel art. You just grind away at the medium you want to master and that's how you make your best work in it.