Sup, I'm some random dude who plays Shaco support daily, and I must say, he's a pretty devastating support! When I first thought of going shaco support as a joke, I didn't expect much, until I noticed how strong and fun it is, even after the laning phase, he doesn't go around his adc like it's his baby, instead he hides in jungles, split pushing, and 80% of the time getting away or even killing the enemy when it comes to stop him.

The runes are pretty basic, the essential part in my opinion is the 10% cdr.It provides you with the perfect amount of cdr with the items you're going to be using.
Everything else explains itself.

The masteries are pretty basic too, the essential part is meditation, it just works so well with this build, and basically is a mini chalice of harmony, works really well with RoA.

Frost Queen's Claim
In my opinion, best support item, gives you everything you need in the start, lots of gold too! The ghosts are great for checking out for incoming enemies or slowing them in a chase.

Where's the rest?

I'm really tired, it's the middle of the night, I'll finish this later :p