While I am really not that fond of it myself, I have to admit that the Interstellar Gateway habitat is well worth buying! Not only does it hold 4 dragons, but it is also a 3 colour habitat - black, blue and purple
On sale right now for 250 gold, cheaper than the other 3 color habitats, and can hold 1 more dragon. I've bought a couple. They go well with the black sands habitats.
Here's my current set up (need to save up coins to get more black sands but this is it for now)