Of the major improvements I've made it is:
Overhead lighting, diffused lighting if possible, white walls and tasks lighting all help Tremendously in working toward a good well lit shop without shadows. I'm constantly improving on mine depending on where in the shop I work most often.
I like a color range of 3k but most overhead lighting will be 4-5k.
I like the walls to be white not beige and bright bright white at that.
Dark ceilings absorb light, so put something that reflects back if possible.
Both my shops went from being dungeonesk to being like a photo studio pretty quickly.
LED bulbs are getting pretty decent now and so I've been able to use entirely LED. I generally opt for the brightest possible bulb for each fixture.