Are the puckers on the body part (because the neck band isn't quite stretched enough)?
If you machine with the neck band on top and body underneath the feed dogs should take care of the slight excess. I think puckers most often occur as you are going round the most curved part of the neckline. I use copious pins and as I'm going round the curved bit I stop frequently to make sure the bodice fabric is laying flat on the machine bed and not lagging behind the stitching. I keep my right hand underneath the 2 layers in front of the presser foot so that I can feel that it is flat and there are no little wrinkles heading for the needle.