By farm I mean use thief on a wild Pokemon to get items, like Pelliper and the lucky egg. Please include the item and Pokemon.
I believe these two links will help you out:
http://www.serebii.net/omegarubyalphasapphire/holditems.shtml
http://www.serebii.net/omegarubyalphasapphire/dexnavitems.shtml
You can get any of these items. I recommend using a Butterfree with Compound Eyes and teach it Theif.
Hope I helped!