If you do not put effort into your cover (not bothering to even add a title to the cover, etc.) readers will assume you didn't put effort into the plot either.
You don't have to be a graphic goddess to make a good cover, the cover could be as simple as you want it to be. And if you are clueless on editing or adding texts to photos; request a cover from a cover shop! There are several cover shops on wattpad that ask nothing but a follow in return.