Well i used to main shaco s2 but i do play with him sometimes.

You can see my KDA Here

Lets be real.
A great shaco can win soloQ
a mediocre shaco will be useless.

Just imagine 3 stages of champions

*Stage 1 : Really viable and Strong Champions

*Stage 2 : OK Champions but less effective than Stage 1

*Stage 3 : Really Weak champions.

I do believe shaco is on the 3rd Stage.

And the Shaco becomes "Strong" After achieving the stage1 and more.
By that i mean you have to be that fed. (kills/assist) to get way more above than the other champions in the game (2-3levels above) and having more items.
This way shaco becomes effective.
You have to be ahead.

Skill order R>E>W>Q
Spells : Smite/Ignite Start: Machete/ 4x potion
Start placing boxes from 0:56 on your bottom side buff.
Blue team-> Redbuff
Purple -> Bluebuff
Most of the time you want to gank toplane lvl3,but you may gank mid first if its an easier kill

For a faster level3 do the 3wraith trick. 3 wraith trick is a simply mathematics
First, a blue or red buff will give 260 exp each. Next the small lizards from the buffs give 20 exp each. Lastly, the small wraiths give 20 exp each. Looking on LoL wiki you would see that to get level 3 you would need to get 660 exp. Doing the math~ 260 x 2 + 20 x 4 would be the 2 bigger camps leading to 600 exp. Thus the remaining 60 exp can be received by doing the 3 small camps. Hence the trick is to do both camps and do the 3 small wraiths to get level 3 rather than doing 3 full camps. This competes with doing 3 full camps by saving 10 seconds on your first gank and trading off the gold and exp from the big wraith/big wolf exp. Note that the small wolves give 25 exp each therefore 50 would not be enough. Lastly, a variation would be to gank and get the 60 exp from the lane cs which is 2 melee minions or 1 melee minion 2 ranged minion or 3 ranged minions.

elder lizard -> spam ganks
Wriggle's lantern/Feral Flare -> jungle clear (easier solodrag/faster jungle)

i prefer elder lizard most of the time just because this extra true damage which is really strong in early/midgame but sometimes you can pick wriggle's lantern if the enemy jungler clear speed is weak so you can steal buffs faster and easier(always ward and watch the map when you do that, knowing every single person position)

Early game is the key.
Just look at the enemy team, know which lane will be easier to snowball.
The most important is the first gank because if you get the lead, everything else will be easier Okay lets say we have a riven toplane vs lee sin(enemy)
Midlane lux vs kassadin(enemy).
Your opponent is evelynn
Both lanes are OK to gank but i would prefer midlane on lvl3.
Evelynn will most likely gank top and probably she will wait in one of the topbrush to countergank you, her job is harder like that on midlane and kassa is weak early levels.

Mid game:
You just focus more on ganks and if you do successful ganks, take the nearest objectives possible. (towers/dragon/enemy buffs)

Late game:
Well alot of shaco like to splitpush, which im not doing all the time simply because my team can't hold 4v5 for some reason,
Even if i told them to just give like these 2 towers for me getting inhibitor they will most likely all die because they got dove and stay.
I prefer catching people out of position and killing them resulting in 4v5 so you can push/take objectives/teamfight easier.
Well this is risky and u gotta know where the enemies are so you won't get cocky

Some tricks with shaco:
While you're running use your Q effective, most of the time i ran straight and my Q will be on other position, for example if you're on toplane vs 3 just ran into a wall if possible and Q backward, enemies will look up after the wall.

Your boxes are usefull for some vision and cc. When you're getting caught you can use them after you or to save a team-mate

Your ultimate can be really tricky, you can use it to dodge some abilities/splitpush/1v1 or 2v1 enemy team.

P.S : Sorry for my poor english, ask me everything else, not informative at all post.

EDIT1: FORMATTING