I really want to improve my skills!

[Cobalt Blue]

step 1 of high level sprite skill:
colors.
Mix your colors and hue shift them, and don't be afraid to use other colors like using blue and adding a hint of green there.

good luck on becoming the high level sprite skill dude/man/master

step 1 of good tier criticism: explain any term you may use, taking into consideration the person you are criticizing might not be familiar with it.

provide examples, and elaborate as much as posible, in order to make your comment as useful as posible, rather than simply making it for the sake of posting -wich is as bad as simply saying "fix it"-

and most important: aim your comment towards what OP really needs, understanding at wich level OP works. you cant ask him to learn hue shifting or antialiasing when he barely understands the basics of proper shading and jagged lineart evasion.