Cannot see preview of 'Wave' effect

Change the colors of the transparency checkers in the settings.

Try adding a layer below it that is a solid color, like black, and then making your current layer and the solid black layer a Smart Object. When you apply Wave to the Smart Object, you'll be able to see it better. After you apply the filter, then you can double-click on the Smart Object to open it up, hide or delete that solid black layer, and save. When you go back to the main document that black layer will be gone and the Wave filter will be applied to your content that has a transparent background.