Shaco is one of the most naturally mobile champions in the game, and arguably doesn't need Flash because of it. Run Ignite instead, allowing you to amplify your burst assassination playstyle, and providing you with more control in the earlier stages of the game. Shaco lives to snowball the early game.

Jungle Pathing
Shaco has fairly flexible jungle pathing, but currently, his optimal clear starts blue buff, with a decent leash. If getting a leash, Drop two Jack In The Boxes next to the blue buff spawn, starting at 0:41. Drop the next one outside the spawn range of the Wolves camp, to pull wolves into later. Place your 4th box next to the Gromp spawn. Proceed to take Blue without using Smite, then take Gromp with Smite. Continue to wolves, and with good use of kiting and Backstab, you should be able to complete a full clear from here. Optionally, after wolves, take Red buff with Smite, and go for an early gank.

Playstyle
Shaco's early fighting is quite strong, but later in the game, you'll look to abuse terrain, get the drop on squishy targets, attempt to pop them with your Deceive + Backstab + Tiamat + Two-Shiv Poison combo, and Hallucinate combo. If positioning of your team is good, you may continue to scrap it out from there, or kite back, distracting with the Hallucinate clone, and leaving Jack In The Boxes in your wake, in an attempt to catch people off-guard for another burst combo when your cooldowns have been refreshed.

Items
Hunter's Machete is your opening item. Use it to clear. Don't upgrade it, however. Shaco has other items that are more important to rush, in order to gain jungle control as quickly as possible, and late game, none of the jungle item options are particularly good on Shaco.
Rush Priority
Tiamat is your first-base goal on Shaco. It allows you to clear jungle incredibly quickly and safely, and provides you with a great deal of scrapping potential.
Berserker's Greaves amplify your clear speed and early control, and scale your clone's damage as well. They're notably strong on Shaco.
Sheen is your go-to burst item. It'll allow your ganks to really pack an up-front punch, and gives you a bit of mana sustain between blue buffs.
Phage is a higher priority than Sheen against tankier junglers and solo laners. You lose some up-front burst, but gain chasing and scrapping power. Build it if even or behind. Otherwise, go for Sheen first.
Core Items
Trinity Force is the single best item on Shaco. He makes really good use of all the stats on the item, particularly the added burst from the Spellblade passive.
Titanic Hydra amplifies Shaco's burst even further via the active, and transforms Shaco from a glass assassin to a bursty bruiser type champion, which suits him far better, later in the game.
Dead Man's Plate, though not strictly core, is probably the best defensive item on Shaco. It provides him with additional mobility, on top of a good defensive stat distribution, and the Crushing Blow slow allows him to get extra auto attacks off more easily, when he jumps on a target, and then kite away in safety more easily, if he doesn't out-right kill them. You'll typically build this 5th or 6th, rather than right after Titanic Hydra.
Other Strong Items
Ninja Tabi are your boot options against auto-attack heavy comps, particularly if you're needing to front-line a bit more in your team comp. Berserker's Greaves are incredible on Shaco, but in many cases, Ninja Tabi provide enough damage reduction to be a compelling case.
Mercury's Treads are only good when you absolutely need the tenacity.
Maw of Malmortius is a great item to build after Titanic Hydra, mage comps. Both the passives can be deceptively strong, and allow you to turn scraps around, and the AD, CDR, and MR are all welcome stats.
Guardian Angel is an excellent 4th - 6th item. Build it if you need defense, and are fighting and pressing advantages with your team. Don't build it if you're splitting, don't need tank stats desperately, or aren't diving carries.
Blade of the Ruined King is an excellent damage item to build roughly after Titanic Hydra. It provides Shaco with sustain, a bit more burst, and incredible sustained DPS, particularly against tanks and objectives such as Dragon and Baron.
Edge of Night is a decent damage alternative to Maw of Malmortius, particularly in conjunction with Duskblade of Draktharr. Statistically, it's not as strong, as Shaco does decent mixed damage, and it doesn't have the CDR, but the active can allow you to sneak into enemy back lines for assassinations without being locked up by CC.
Duskblade of Draktharr is a decent assassination playstyle item on Shaco, particularly in conjunction with Edge of Night and/or Youmuu's Ghostblade. Again, the stats aren't ideal, because Shaco does a mix of damage, but the Nightstalker passive synergizes incredible well with Shaco's assassin playstyle, and should definitely be considered, particularly on damage heavy builds vs squishy teams.
Hextech Gunblade is a burst-heavy alternative to Blade of the Ruined King. With the recent changes to Shaco in patch 7.7, it might be slightly stronger than it was previously. Worth considering after Titanic Hydra for burst damage and sustain.
Mortal Reminder is a solid option against tank comps, if you're playing more of a DPS role for your team. Particularly good with Blade of the Ruined King.
Lord Dominik's Regards is a solid option against armor-heavy comps, particularly in conjunction with Duskblade of Draktharr.
Ravenous Hydra is a rare alternative to Titanic Hydra. Only build this if you're snowballing and/or planning to split push, preferably against tankier opponents. Against squishy opponents, Titanic Hydra still tends to be stronger due to the burst threat.
Youmuu's Ghostblade is another rare build, if snowballing. It's usually only considered in conjunction with Duskblade of Draktharr, and usually in place of Edge of Night, rather than in conjunction, as Shaco typically wants at least one defense item late game.