I'd probably recommend seeing if you can talk shop with someone in the pixel projects forum, but generally speaking, I like to divide my overworlds into body types(tall, muscular, etc), and then reduce characters of that body type into 'dolls' (naked-ish figures without any hair) that can then be added onto fairly easily. Once you're at that stage, you can draw clothes, hair, facial details, whatever right over the doll and adjust as your taste dictates, and at the end they'll look consistent with one another(which really is the best you can hope for when doing a game project).
Dont overthink it. Overworld sprites dont need much detail at all. Hell for one of my sprites I took Professor Oak, cut off some of his hair, and pasted Blaines mustache on him, then did a little shadowing work to make it look natural. It really is only as hard as you make it
I'd start with a blank character sprite. Draw out a character with ms paint or pencil, then focus on each element of the character, whilst zooming out to keep checking the scale and overall craftsmanship.