Welcome to Pixelation
My 2 main concerns are the solid black outlines and the colourcount.
It looks like you have a base outline and then you just colour that with whatever colours.
This bit of the head in yours has 130 colours (with the bg) --- mine has 16 with bg
If you look at what I did you can see that firstly I removed the black outline and corrected the lightsource, straight from the top. Not that nice, slightly asymmetrical would be better but for the sake of the edit it will suffice.
Mainly there are 4 colourramps in the head:
- Skin
- Cap
- Golden rims
- Glasses
The skin can share the darker tones with the gold (the 2 brightest shades after the white for each are unique the darker colours after that are shared.
The brighter colours of the cap can be shared with dark colours of the skin and to antialias between the both as I did around the cheek area.
Now this leaves the glasses, for which i have 3 colours left, 2 of which also occur on the leather as highlights and the darker desaturated purpelish colour on the leather is in the glasses as well. We call this general technique tinting or rampmixing. When working with low colourcount and not for game with swapable palettes it is a good practise to do this, to maximise the use of the colours at hand, as well as giving a more unified, coherent look.
I also used som basic dithering to smooth out the transitions on the leather and to give it a kind of texture as well, show that it is a bit rough.
You wondered which tools you could used for pixelart: There is a consensus among many of us that as long as you have full control over every colour, and the placement of every pixel, then your art is pixelart. Any tool that generates new colours for you on it's own, such as soft brushes or layer effects can be considered dirty tools. Some more than others. So you can use the magic wand and similar selection tools as they have nothing to do with manipulation of pixels as such.
Hope this helps, feel free to ask if something is unclear.
Have a nice stay.