Let me expand and clarify on what other people have said.
I personally run
magic pen marks
mp5 per level seals
flat cooldown glyphs
flat ap quints
ignite/ghost (you already have a flash and you are an assassin so you need extra damage)
These are highly customizable and can be changed to reflect your playstyle or your build.
If the enemy team is tanky, build DFG, typically starting with Kage's and boots. Depending on your runes your boots are either going to be Lucidity, Sorce, or Swiftness (Not mobility! Ever!)
Next get Rabadons and consider Voidstaff if they are stacking MR.
If the enemy team is squishy, you will want to burst them as much as possible. Start with Blasting Rod, boots and pots and get Rabadons asap. I personally dont get DFG unless they have 3k+ health but I might change this in the future.
One of my biggest pet peeves about inexperienced Shaco players is their poor placement of JitBs. DON'T stack them all on top of each other; this is a gamble and a waste.
Sure, if it works it will guarantee you a kill BUT the direction the fear sends them is completely random, you have just as high of a chance of fearing them away from your JitBs as you do towards.
Imo, JitBs should only be placed in the following three patterns:
1. As wards, primarily utilizing their vision and locking down control of the 'jungle'. This lets you see everywhere that people go, gives you free harass, and makes them scared to be aggressive. This style is primarily used when the enemies are roaming.
2. On key locations in clusters of two. JitB's scale at .25 of your ap, this means that two stacked boxes have to each shoot twice to do 100% of your AP. This is a huge amount of damage but if the fear sends them the wrong way, no big deal; it was only two boxes.
Never, ever, ever put your boxes on top of the speed boost, that is for Teemo to do. This will only ever make it so that the fear speeds them away, instead, place them before the speed boost while they are still slow.
3. In a grid or concave pattern. This is the closest that I will typically get to stacking my boxes on top of each other, the only difference here is that if the fear sends them the wrong direction you only lose one or two boxes. If they fear is lucky you will chain fear them into your armada.
I use this when I am trying to hold a node that the enemy team wants badly and I am sure of the route which they will take.
Remember, your boxes are always wards, always cc, and often a potential nuke, treat them as such.
They watch your back while you ninja nodes, they save your teammate with their cc, they cannot be ignored.
Oracles is not a hard counter, you just need to place your boxes even smarter. Often, simply putting them at the edge of a bush will do, by the time they see them it will be too late. A lesser used strategy is to put them in plain sight, right around the corner. This will hides your boxes in fog of war and takes many people by surprise. Intelligent placement will always beat wards.
Also, ward your **** nodes, a lucky fear will send them back to your turret. The combination of your box and the turret can often take out someone who would bd.
Shiv is your primary harass/nuke. If someone is capping your node but you are intimidated by their damage (Jax, Akali, Talon, etc) throw a JitB at your own feet and fling a shiv at them. If they jump on you simply deceive away while they are feared.
Also, use it to help out your darn teammates. If they are trying to chase someone down, the slow can be invaluable.
1. You are an assassin! Play like one. People will rage at you for KSing or for "not helping in fights" (aka I over extended against three people and I want you to save my ass) but you are a nuker, not an auto attacker. Blow your load and poof away.
2. You are not an auto attacker! Ergo, if you do not have your **** together you are screwing your teammates! Make sure that you have your god**** boxes where they need to be, make sure that you are harassing with shiv, make sure that you are using your clones death to the fullest potential. If you are not constantly doing something, you are a dead weight.
3. Rylias and JitBs dont work together :' (
I have less experience here, my word is not law.
21/8/1 (8 in armor/mr/dodge, 1 in ghost)
armor pen marks
flat armor seals
flat cooldown glyphs
armor pen quints
ignite/ghost or exhaust/ghost
Sheen mother ****er! The AP + AD + mana from this item is so helpful in your early game. This is not an option, this is a go to item!
Brutalizer. Armor pen + CDR + builds into crit and movement speed Ghostblade. What's not to love? This was made for Shaco.
Infinity Edge + Deceive = pain
I have heard good things about Atmogs Shaco, but I have yet to try it.
1. Your only safe way to get out is also your initiator (facepalm) pick your situations wisely.
2. Dodge things by popping your ult. Kass silence orb in flight? No problem, pop ult and it disappears.
My brain has shut off, I can no longer type things for Shaco, I might update this later. Willing to answer questions.