It should come with everything you need.
The system will shake the enclosure if you dont secure the tubing, and while there are many ways to secure it, the tubing clips make it very easy.
So you might think about adding some of those.
Mistkings "rain attachment" is just a nozzle, supported by tubing on top of the enclosure.
I made one for myself, and did not find it very useful, as it took up too much space on the top of the enclosure, and did not provide me with the results I wanted.
I just aim nozzles at foliage, that is placed high up in the enclosure (pothos vines/leaves) and the water drips down off of that, creating a rain effect.
Thats just what worked best for me though.