If you have any Pokemon with maxed-out EVs, then you can do the Secret Super Training levels, and you can get Dusk Stones from them. --- R.I.P. Pokemon Cycle Fact: Things are so much better when taken at face value.
Strictly speaking, you can get a Dusk Stone as soon as you get your first pokemon. --- Currently playing: Pokemon Y, Xenoblade Chronicles, 3DS FC: 2277-7562-5299 All bow down to your Steel type overlords!
It isn't too bad to get. It took me maybe 4 rounds of it to get one. My friend said he found it on his second. So either we're both really lucky or it's fairly common. --- In case of a Zombie Apocalypse, follow me! Add my 3DS FC: 2535-4356-9059 Name:Marcx