Pros:

One Of the best escapers
Best deceiver
One of the best ks champions
Very good pusher
One of the best gankers
Easy kills if you get fed at start
Really fun to play

Cons:

Very Squishy
If Your team are noobs you cant get the game alone with shaco
Elixir or wards can destroy all the fun
Hard to master
Your team may flame on you because you do many ks

What i do here with crit chance runes is to get some easy kills with shaco's ability backstab what we will do in this guide is to ks but when u need a kill and you are solo the only way to kill the opponent is to confuse them with fast moves when you move fast the other gets confused and probably try to run back but if they do that on shaco they are gonna die because as you hit them they get slow and only with one crit from the rune page one ignite one deceive and one two-shiv poison you will have an easy early game kill.

I put 21 at offence just for damage but i put also 9 at utily which it could be at defence for some dodge but since i didnt put any dodge runes in this guide i believe that this extra experience gonna help you a lot because after lvl 3 you will propably go many gangs and wont have time to xp and greed is a good boost at ealy game as you dont get many creeps and you need fast gold to buy B.F. sword also with the 9 ultility points you go lvl2 after killing blue buff at the start.

This guide and this item build are for solo queue because as youve seen i only have damage items no hp or armor and magic resist which is not so good.If you want you can also go for banshee instead of Bloodthirster or warmogs this would keep you alive but as i said this is a ks guide so you dont have any reason for any survivability and also you have your illusion to tank.

i use ignite and ghost both for ksing, ghost is a really nice spell for shaco and it is a must as you can gang with it very effectively and get at 90% a kill every time you have ghost

So this is the nice part of the guide you have to do nothing but w8 for your team to start a fight you see who is dying and as you have opened ghost you use deceive and start hitting because as he dies he tries to run so you get 20% more damage from backstab and when the time is right use ignite and two-shiv poison to get your kill.Now if you go gang someone at 1v1 i figured out the best thing on shaco which is ghost+deceive+hallucinate if you use deceive and then hallucinate you will see that your illusion came out but you are still stealthed, what you do here is make the opponent hit the illusion and be sure that he will because he thinks it is you as it is the only one there and you are still stealthed now after he starts hitting the illusion you go behind him and hit your critical you get by deceive then continue to hit him but dont use your two-shiv poison as we need its passive for slow, then you use ignite and he starts run then you must continue hit him and then the right time when you cant get more hits you use two-shiv poison to finish him also have in mind that you used ghost in the start of the fight and as shaco has a lot of damage he should start running at the beggining and with slow and ghost you will probably land many backstabs and with ignite doing some true damage he will be probably be dead before you throw your two-shiv poison so what you do here is:Ghost->deceive->Hallucinate->backstab->ignite->many hits->and two-shiv poison for last hit.