Agreed, makeup colors make a huge difference! It's also a good idea with makeup to not try to match the eye color to the eyeshadow or eyeliner. A different but complementary shade tends to highlight the eyes' natural color more, and that's really important, especially if you have a sim with small or squished up eyes. Oh, and the opacity sliders are also important. They almost always look fake and caked on at max, so test at sliding them down and see where it looks best.
Also, if you extend the eyelashes (not sure if it's only available in CAS or directly from the mirror) sometimes that can really help a sim. I don't consider it body editing as much as using one of those "volumizing" mascaras.