Current ranking: Platinum II
Season 5 ranking: Diamond V
Hello
I started playing Shaco in season 5 where I decided I wanted to main him for the reasons being, that he's hard to master, not played so often which makes it less likely that people are going to pick/ban him, and are likely not familiar with playing against Shaco.
In season 5 i was placed in Silver 1 after placements. I ended the season being Diamond 5, with mainly playing Shaco and teaching myself how to deal with certain matchups and situations you will come across. Hopefully I manage to teach you, so you can control the power of the clown.
At the end of season 5 I was placed in top 100 best Shaco player in the world (according to www.lolskill.net).

As mentioned before, Shaco is hard to master. You will most likely not gain success straight away if you jump into ranked with him. I suggest practicing the start in custom games by yourself, then take your practice into normal games, get the feeling for it.

You may read this and think " Shaco is not hard, that's nonsense". People who has that mindset, just havent tried to play him, or the Shaco players they have encountered just makes it look easy, which is the greatest compliment you can get. But I will say this, Shaco is easy if you put in the work early game. Shaco is not fun if you get behind, so dont slack early game!

Season 5:

Season 6 (12-4-2016):

At the moment I am ranked around being the 500th best Shaco in the world, but I'm hoping to get back in top 100 within this season.

My most recent games as Shaco:

When it comes to skin, always use Masked Shaco if you want to tryhard. The reason for that, is the smoke which appears after using Deceive, is purple when using Masked Shaco, and other skins like Wild Card Shaco has orange smoke. Because the smoke is visible for players even when used outside fog of war, having a dark smoke color is best, cause it blends in more with the rest outside fog of war, cause it is black/gray.

Masked Shaco Smoke animation:

Wild Card Shaco Smoke animation:

Masked Shaco is the only skin with the purple smoke animation, rest of the skins got a orange colored smoke.

So how can a different smoke animation win you the game? Getting ahead early game helps snowballing a lot, the way you get ahead is usually by ganking and killing opponents. Having a less visible smoke animation, gives your gank better odds of being successful. If the enemy is noticing your orange smoke animation, will the player start walk backwards untill you are visible. Gank failed. Also for late game, it is easier to pick people off if you are not spotted. Killing enemy AD Carry late game can be game winning. Just examples of how it benefits having Masked Shaco skin. So a little bit pay-to-win.

Counter jungling is a risky move. You have to keep certain things in mind when you feel like ruining the other junglers day:
1) Are you stronger than him? ward his jungle keep track of his movement, and strike him at the camp you assume he is possibly at.
2) are you not stronger than him? pay attention to the mini map, if he show himself at bottom lane, steal his top side jungle to make him pay for the gank and get deep vision while u are in there (good time to make use of the Vision Ward which you of course bought after you visited your base).

Statikk Shiv
"Poor mans Trinity Force". One of my prefered item, since it's low cost for high amount of burst dmg and attack speed. Usually finished after Warrior Enchantment and Ravenous Hydra which is Core.

Stalker's Blade vs Skirmisher's Sabre
I prefer Stalker's Blade cause you are not looking to fight tanks with lots of hp. Your priority is champions with next no tanky stats. If you happen to encounter a tank and you just want to run, adding a slow to them is helpful rather than reducing your damage taken from them which may could have been avoided completely cause of a slow.

Dead Man's Plate
Build vs. heavy ad teams. I usually don't build for 2 reason. 1) i dont run into many heavy ad teams. 2) i usually get far ahead early game vs full ad teams, so i take greedy items like Statikk Shiv, Trinity Force or something like that over it to push my lead. Build Dead Man's Plate if you feel the need to respect the damage output from them and you struggle with reaching your target.

Trinity Force
GOD TIER ITEM (atleast for my playstyle). Lots of damage, mobility which stacks nicely with
Stormraider's Surge and gives a bit of tanky stats. Fits well with Sterak's Gage Cause it's extra damage is based on base attack damage, which Sterak's Gage increase by like 25. Trinity Force on hit damage is 2x your base attack damage, so the extra damage from Sterak's Gage is 50 + the crit from your Q which deals 220% of normal, so it's 110 intial bonus damage from buying a tanky item.

Guardian Angel
Good end game item. Purchase if you feel like you are on a kamikaze mission late game, take out your target and then die and potentially get out after being revived.

Sterak's Gage
Explained at the Trinity Force section.

Maw of Malmortius
Good standard item to build if the enemy has threatning ap burst damage like Annie, Syndra etc. I usually build this as 3rd item if I don't find it possible for me to bully them with other offensive items.

Youmuu's Ghostblade
Nice armor penetration, good movement speed boost which can be used to travel extra distance while stealthed from Deceive, and get a few extra auto attacks in. I build this after Trinity Force/ Statikk Shiv (depends on how fed i am).

Mercurial Scimitar
Heavy burst and cc team with like champions like Morgana, where cc will be your death.
Can also be used to avoid Twisted Fate's ult to gain vision on you, makes it easier to get away while stealthed.

Ravenous Hydra
Standard item, always get this. Excellent waveclear, jungle clear, sustain and active effect to do more burst damage.

Infinity Edge
If you are super far ahead and want to experiment with other high damage items. I'd say a rule about this item is:
"buy it when you are so far ahead that your next item has no impact on the outcome of the game"

Ionian Boots of Lucidity vs Ninja Tabi vs Mercury's Treads
Ionian Boots of Lucidity if you are ahead and you dont feel the need to respect either ad or ap damage. Gives nice cooldown reduction.
Ninja Tabi: vs heavy ad and auto attack based champions like Jax, Caitlyn, Xin Zhao etc.
Mercury's Treads: vs. heavy CC team.

Vision Ward
GET YOUR CHEAP AS BACK TO THE STORE AND GET A Vision Ward! Do yourself and your team a favor and buy a damn Vision Ward for 75 gold. I'm not christian but Jesus man...
I ALWAYS buy a Vision Ward first time I head back to base. Either I use it to get deep vision in the enemies jungle or i use it for soloing drake safely after i hit lvl 6.

Oracle Lens
Keep Stealth Ward untill level 9, then swap it to Oracle Lens.

Two-Shiv Poison > Deceive > Ravenous Hydra active ability
A neat way to get more done at very little time, is to use Two-Shiv Poison before you strike with your Deceive crit.
example:
You are chasing someone down who is within your Two-Shiv Poison range, use it then Deceive to hit them with the crit right after. the Two-Shiv Poison travels slow, so it arrives at the same time as you do even when you use it before Deceive, followed up by Ravenous Hydra active ability.

Deceive > Two-Shiv Poison > Deceive crit auto attack > Ravenous Hydra active ability
Make your Two-Shiv Poison land at the same time as your crit.

example: Deceive to your target, break stealth by using Two-Shiv Poison then auto attack for the crit.
Especially good vs. Sivir because she will not be given time to spell shield Two-Shiv Poison

When it comes to jungle start, I highly suggest you ask you team to cover, especially your mid laner, since the most common early game invade against SHACO happens through the bushes closest to mid lane. Ask for cover, mostly so the enemy don't spot you. If they notice the way you place the boxes, a guy with knowledge about SHACO will call red alarm and tell their team about your invade on them. Usually people are not that smart about it, so dont expect it, but it is possible, so be cautious.

IMPORTANT MUST-READ-NOTE!!!!!!
When enemy bot lane is leashing for their jungle, you should spot them on at map between 1:54-1:56. If you do that, you know the enemy jungler didnt get a smiteless leash, which is important for when you fight him about the buff you invade when you start blue side.

Also pay attention to where bot lane is returning to lane from. If they walk from the river to the lane, it means the jungler got a leash on blue buff, which makes you unable to steal that. In that case, you either go gank mid lane or you are persistent and look for him at wolves/gromp and fight him for the buff he got and the camp. If you notice their team leaving lanes to back him up, tales between your legs and retreat, be creative with your Q for escape.

Blue side (fun side!)
You gotta love blue side, cause it can give you insane map pressure with the route I use. It is high risk high reward, just like SHACO is meant to be played.
(Please read the notes about the steps on the picture before jumping into it)
#1:
You start at your red buff. Place 4x Jack In The Box behind the big one, which you should do around 0:40. DO NOT DO IT 0:39 or before that! Your Jack In The Box last for 1 minute, and the buffs spawn at 1:40, so 0:40 is the earliest you can do it.

You want to take as little damage as possible. You tank the first hit, then when the big guy is mid auto attack animation for his 2nd attack, you walk backwards to lose aggro onto the boxes and you start attacking again. Or you can tank the 2nd attack on purpose and then walk back after the hit so the boxes get aggro, up to you.

When the big dude is dead, start attacking the little dude TO THE RIGHT (it will take 4 hit to kill him). While you do that, you place a Jack In The Box at the little guy to the left, when u have finished the right one, you give the left dude 1 hit and you start moving to the river, and over to #2. It is the most efficient start, which will make you be at river around 1:57 in game time.

#2:
The invade. This is where you invest your effort early on, and you rely on getting the blue buff from your enemy! You use your Deceive to get over the wall. Analyze the situation when you Deceive over the wall. If the buff is like 900 hp, walk into the bush and wait for it to drop a bit, around 600 hp or untill you fear the enemy jungler is going to find you by accidently walking into the bush. Also pay attention to if the enemy jungle is running away after you get over the wall, it means you are spotted by a ward somewhere, finish the buff if it's hp is between 1-700 if higher, get out of there! you will not have the time to finish it before the team will collapse on you.

When you engage on the enemy jungler in a invade situation place the box behind the jungle to cut off their escape route and fight on top of the box if he tries to kill you.
Note: clear the camp if possible, it's nice to have the timer on enemies buffs.

#3:
Your next move now depends on how #2 went. If you killed the enemy jungler and/or took the blue buff, follow the purple route which will lead you to the enemy jungle's red buff, but first look for a gank mid lane, doesnt need to be a kill, just applying some damage can be help enough sometimes. Don't be scared of casually walking cross the lane, as long as you make them think you are heading to your own jungle, by walking towards your own jungle untill you hit the bush at the lane, then you make your way to the enemies jungle to continue pressure on the jungler.

If you didn't encounter the enemy jungle, but noticed he didn't start at his blue buff for some reason, take his gromp aswell, then look for a gank at bot lane, like so:
#4:
Head to the enemies red buff and do as the picture illustrates, which is placing a Stealth Ward at the very end of the bush to grant vision of the bush and the entire camp , then Deceive to the krugs and steal the big one. Kill the little one if it makes you hit level 3, otherwise leave it.
#5:
Now you should be at the krugs, waiting for the enemy jungler to appear his red buff and start attempting to clear it. while you wait, look at your top lane. If you are 100% sure you can get a kill, do it rather than invading, if it's only 90% successful, be patient and wait for the enemy jungler. Again, approach the enemy jungler with a box behind him to cut off his escape route, keep an eye on the red buffs HP as you are fighting him, you also don't want to start the fight while the buff is almost in Smite range, cause then u basically wasted your time. engage at around 700-800 hp on the buff. If it was successful, you got the red buff and killed or brought the jungler too low to return to his jungle, take his raptors aswell, then head to your own jungle or look to gank top or mid.

Invading with red side start:
#1:
Similar to blue buff start, 4x Jack In The Box behind the red buff monster, and clear the rest of the camp as described above.

#2:
Most junglers don't start at their blue buff when playing on blue side. Makes the invade easy. Follow the route on the map, Deceive over the wall and start clearing the blue buff camp. Remember to place a Stealth Ward over the wall to potentially spot the enemy jungler approaching.

#3:
If you are done with the blue buff, and you have not spotted the enemy jungler, take the gromp.
Note: Don't use Jack In The Box when only the 2 small ones at the blue is remaining, save it for taking the gromp to stay healthy.

After the gromp has been feared by Jack In The Box move away from the gromp and let the box tank 2 attacks so it dies. Smite gromp, and take either route for #4.

#4: Look to either gank top lane or mid lane. If both are gankable, take top lane because it's closest to the gromp which you just finished. If top is not gankable, make your way to mid lane, then to your bottom side jungle after the gank if you are healthy enough and clear all 3 camps.

Team fightning as Shaco

It's mid/late game, teams has started to group up. How do you keep yourself useful?
You don't want to give up your position unless you need to. You not showing on the map create passive pressure on the enemy team. If you have the feeling a team fight is about to occour, clear vision in the area you would like to engage from. You don't want to be spotted if you can avoid it.
You should NOT be the one engaging the fights, unless you are using the kamikaze build and are 100% sure that you can kill one of them before the others can react. Usually, you wait for either of the team to start the fight, keep your eyes on the enemy adc, who will most of the time be behind his team. Deceive through the enemies, make me proud and use the damage combo I taught you.

Applying pressure on the map

Pressure the map, clear wards around objectives like baron, drake and your own jungle. keep the lanes pushing. Always be on the look making a potential pick.
Lets say you push bottom lane, the wave starts building up and at last it will reach get close to the enemies tower, think ahead and get near that wave, because someone with a greedy mind like an AD Carry will likely appear to clear that wave. While he is doing that, engage on him and kill him or force his summoners.

Deceive: Can juke opponents to think you went over a wall by walking up to the wall but Deceive backwards. Can be used in many many situations.
If you failed your gank: Walk out of fog of war, then Deceive back into the lane. People don't expect it usually.
Look to engage ganks: Be creative, find a wall to Deceive to engage your gank, makes you less like to be spotted by a ward.

Jack In The Box:
Place these bad boy when:
Running away, to fear enemies.
Split pushing, use them as vision where you want.
Ganking, placing it behind the enemy to cut off escape route like you did when you invaded the jungler.

Hallucinate: Can be used to avoid crucial abilities.
Examples from different champions:
Lux: Can be used to avoid her ult, even if you are hit by her snare.
Elise: Can be used to dodge coccon.
Vi: Avoid her ult.
Zed: you can't avoid the ult, greatly reduce your damage taken and potentially win the 1v1 if you use Hallucinate right after Zed's ult animation is done, and start damaging him.
Vladimir: Can be used to avoid the damage you would take from the his ult if you use Hallucinate just as the debuff is about to expire]]
Karthus: His ult can be avoided by using Hallucinate just as the ult is about to do damage (works like Fizz)

And many many more situations. It some abilities require good timing, and you will not always get it right. Practice!!

Thank you for reading my guide on how to get better at Shaco, this is the first guide I have written, so constructive critism in the comments is appreciated.

I will add more stuff here and there eventually.

Have a good day!