You want step up rings, not step down rings. Step up rings are smaller on the end that screws onto the lens and larger on the end that screws onto the filter. Step down rings cause vignetting.
If using step up rings on a wide or ultra wide lens, you still might see a little vignetting. Some rings are thicker (depth) than others so I always try to find slim profile step up rings. Stacking the rings may cause vignetting depending upon their depth and how many are being used.