Edit: New information has been posted, check July 2014
Here is a Luck guide that I will be doing, Thank Kenny (Darkfear on toucharcade) for the suggestion.
Only one specific armor I have found to have Luck attribute [lv.58-lv.62 Water Dragon set]
It is rare to find Luck runes, mainly because it's Level Pink, and you need luck to find luck. (I know I've said that somewhere else...)
Accessories which have to be Rare or higher, will give you luck. But to find these, easiest way is to gamble.
Now when you have a Rare Accessory, it is highly rare you will get luck on it. Heroic has a higher chance, and with legendary, as hard as it is to find, will have luck attributes most of the time.