Hi there, and welcome to Pixelation.
I just started pixel art a week or two ago, so I am no authority on how to create great pixel art.
But I drew your guy in my own style (60-ish px by 20-ish px), and in showing my process, perhaps you may gain something of use.
so step 1 (left -> right) was just getting the form down to a point where I was okay with how it looked, and adding the base colours to the different parts of the body. When looking at your character, I noticed the colours you chose (especially the hair) were way too saturated. notice the yellows I used for the hair are more toned back.. it hurts the eyes less.
step 2 was adding shadows (no highlights), and fixing little areas of the figure (see right leg & arm). For determining where the shadows should go, I picked an imaginary light source (top left) and added the shadows accordingly, as best I could. They arent perfect - as I don't have much knowledge in light/colour theory - but it's passable, at least in my opinion. The most important thing is to be consistent with your shadows once you've chosen the direction of your light source.
step 3, as per my style, involves outlining the character in black. I think it really makes the character pop aesthetically, and also helps separate the character from background elements for better readability.
anyway, I hope that helped a little, seeing my process. it's pretty basic I think.
Good luck in your efforts to learn pixel art!
EDIT:
I just wanted to add that good pixel art takes time. it takes even longer when you're a beginner. you have to be smart about where you're placing your pixels and really be meticulous about it. my drawing of your character probably took 45 mins.
