to get the clouds moving effects, you need long exposure like a few seconds,
to get this effects with 3 stops ND filter, you need very fast moving clouds and a very dark sky.
usually using a Hoya ND 400, or B+W ND110 is more suitable.
with my experience.. the 3 stop nd is quite useful for moments just before sunset and sunrise. A ten stop nd would be too difficult and long to get a sufficiently bright picture.
But do try to get the ten stop.. it is a nice filter to have and is very fun for minimalistic pictures where things are moving.
Do note there is colour casts of magenta when stacking a few square filters together. It is a normal occurrence and can be corrected with photoshop.