Welcome to Pixelation!
Things you did right:
1 - Not working on white
2 - No dirty tools
3 - Started small
Things you did wrong:
1 - Straight, unmixed ramps
2 - Over-reliance on outlines
3 - Mirrored
4 - Can't tell what he is wearing
5 - Generally flat appearance, no clear light source
6 - Face appears to be copied (not ripped or anything) from various anime RPGs, rather than created with own style/logic
7 - Boring colors/lack thereof
8 - Result of mirroring, but really, really boring pose