You can purchase the standard Storm Puff item in the Scuttle Town shop for 50 gems (as well as the upgrades if you have more gems and some magic jam). Aside from the Storm Puff, I also recommend buying either magic vials or the Magic Fill item so that you can get some magic power. The Storm Puff item is a bit slow and it might take a while to get this achievement, however there's an easy way to do this.
Go to the Pumpkin Fields and you'll find some pillars with some enemies walking on them. Lots of enemies spawn here, so try and create a cloud above a bunch of them. If done right, you should be able to kill at least 5 enemies. When they're dead, walk to the right a bit and go back so that they'll spawn again. Do this for about 2 minutes and you'll have the achievement.