I crocheted a sc washcloth for an intro to crochet class I taught. Not thinking about it beforehand, I am finding that my washcloth needs a little umph - maybe an edging. However, I didn’t consider that when crocheting it so I didn’t account for X amount of stitches. Is there an edging out there that looks nice and works well with an even number of stitches rather than a particular number of stitches? Thanks in advance. 
You could do a crab stitch, a.k.a. reverse single crochet, around the edges. It’s just sc backwards. It works for any number of stitches and gives a nice, finished edge but nothing fancy. I think you would do a round of sc first, then the round of crab stitch.
Yes, that is what I would suggest too…reverse single crochet! That is what I used on my granny square cotton cloth just recently and I think it adds just enough of a finishing touch without taking away from the main design. I also agree that a round of regular single crochet first would make it look even better, especially on a back and forth pattern.
Would love to see a picture!
MGM