Use two ring lights, one on either side of your webcam, to brightly light your face evenly on both sides.
With two 18″ USB extension cords that I run to them, I never have to recharge them (though I can if I want to take them to my laptop away from a plug).
I highly recommend the Qiaya Ring light, currently on eBay at only $15 each. You want this lopsided looking one, not the many out there that are a perfect circle (the one with a bar across the center), which aren’t as bright.

Why the smiling little man to the left of the lens?  As mentioned in a previous post, he reminds me to talk up toward him, as if he were my client, not to the moving image of the real person on the screen.  When we speak while looking at person on our screen, our eyes appear to be looking down.