My biggest pet peeve is not so much makeup, nor is it only limited to WoC, but unfortunately, I seem to notice it more in us darker beauties. It's not taking excellent care of our skin. NOTHING bugs me more than seeing someone who obviously spent a lot of time and effort (and maybe money, you can't always tell) on their makeup and put it on top of sh!tty skin.
Like me, many PoC have a tendency to oily, blackhead prone skin and hyperpigmentation and scarring. I know how hard it is to find good foundation but if your hyperpigmentation is really bad, think about investing in a good foundation - as a last resort get it custom blended. Also, don't forget coverup for under/around the eyes as many darker/olive ladies like me have bad dark circles.
Finally, invest in an effective skincare system - I know a good routine is expensive, so go for less expensive alternatives where possible, but please, exfoliate and keep the oil under control. Shine and blackheads are NOT cute. I agree with the poster above who said that in our culture, spending a lot of money and effort on beauty is considered frivolous, but believe me, most of the celebrities (male and female) we admire don't have 'naturally' beautiful skin, or only use a little cocoa butter or whatever natural remedy they try to convince us of. They spend thousands on chemical peels, lasering, botox, microdermabrasion and prescription-strength skin-care.
Again, this is not only/every WoC, but I seem to see it quite a bit in our community.