If you're going AP, Deathfire is much better than Morello. Just placing boxes and throwing shivs isn't enough: the active actually gives you decent burst. As for AD, it's all mix and match.
I find Mobility to be the most useless boots for Shaco because: 1.) When the fight rolls around you are stuck at 2 move speed without any other benefits from the other boots, and 2.) The time it takes to get the speed bonus back makes it not worth it because you are supposed to be jumping in and out of fights.
Triforce is a great item for AD Shaco because it gives him all the movespeed he needs and makes Deceive/Two Shiv+backstab combo very deadly. I find that a squishy Shaco is not that helpful because all you can do is stay in the fight for a few seconds max while their bruiser/tank just ignores you. It's all down to playstyle and preference really, but I always get Shaco some survivability by the third completed item.
My AD builds would go something like: Mercs/Zerks, Triforce, IE, Youmou's, then depending on their team: Sanguine, Frozen Mallet, Sunfire, Wits End, Black Cleaver, or Odyns Veil.
For AP depending on team I get: Ionian/Sorc, Deathfire, Rabadon, Rylai, Lichbane, then whatever to counter the enemy team with: Abyssal, Void, or Hourglass.
Like I've said it's all down to preference and what your style of play is, but I've found the items I listed as the most effective for myself.
I don't like to play straight AD or AP Shaco, I always play Activateable Item Shaco. Deathfire+Gunblade actives as first two items gives you decent auto damage, good ap, cdr, lifesteal, spell vamp, and lastly but most importantly two damage actives on top of Two Shiv for amazing burst.