Well this is my first build and it isn't very in-depth. I will only be covering item build. My item build is a tanky-ish/DPS build for quickly getting in doing some damage and retreating.(I generally only play 3v3 now, so it would be interesting to see how well this works 5v5)
To me WuKong feels a lot like Shaco (maybe because he has invisible and clone) but by mid-late game he becomes a lot tankier than I usually get Shaco.
Although you will get some good HP WuKong still tends to drop quite quickly that why it's important to get in and out quickly and not be tanking for your team (although your clone can tank :P) and if this build doesn't work for you... you fail? :3

'Crushing Blow'
This is great if you and/or your team gank a enemy by surprise it has a good damage output and it lowers their defense which is great if you have another DPS on your team and even if not.
'Decoy'
If engaging in a fight where we don't have the element of surprise I will try and save this move for getting away or distracting our opponents if a low team member is fleaing.
'Nimbus Strike'
This move is more useful as a distance closing ability, very similar to Yi. The damage is not great but its good for catching those low luckers that think they are safe, it's also good because I don't ignite.
'Cyclone'
When first unlocked the base damage is only 20 but you will find at level 2 there is a significant jump to 100 and again at level 3 to 200, this is great for setting up a good stun-lock if you team isn't quite in reach in some cases it can be good for escaping as well (if decoy is on CD)

I like to start with a Doran's Blade, the HP combined with the HP masteries is good as well as a bit of extra damage.
My choice for boots is Ionian Boots of Lucidity, I find this a good choice because of the CD reduction combination of masteries and Youmuu's Ghostblade this allows you to spam his Q 'Crushing Blow'.
My next item is then a Ruby Crystal which I build into a Phage, the slow, damage and HP is good all-round for him early game.
By now for me WuKong feels a little lackluster with not much lifesteal for healing on minion waves so I like to take Wriggle's Lantern and considering this is a 3v3 guide I find the ward very useful for Dragon or Red Buff.
Next I go straight for a Trinity Force, I generally get the Sheen component first because the passive is great for WuKong.
Next is a Frozen Mallet which I get because I want him to be tanky but still doing some nice damage.
For my last item i usually go for a Atma's Impaler, although you could perhaps go for a Phantom Dancer or Bloodthirster.
And that concludes the item guide :D

WuKong is great at taking down the squishier champs, so if you find yourself laning agaisnt some squishies I like to 'Nimbus Strike' in and follow up with 'Crushing Blow' then simply walk out using 'Decoy' if you have your ultimate follow up with it especially if you have a team member close that can stun or slow. If your sure you can take the kill safely I ultimate then exhaust them to stop them running out (if they are a faster champ)
I will always take Exhaust and Ghost but you can change depending on your playstyle.
If my team is ready I will get close to a group of enemy champions luring them into a gank, then I 'Decoy' hopefully they put some of their abilities on CD then my team and I will re-enter and attempt to ace.
I usually try to convince my team to let me solo (despite resistance) and end up getting a kill or two in a row

It's nice to take 3 Greater Quintessences of Fortitude and a full set of Greater Marks of Fortitude early game this just makes a little too tanky combined with Doran's Blade and masteries while putting out some really nice damage, I also take Greater Seals of Resilience and Greater Glyphs of Warding because it runs good with his passive.

If we are planning to get first blood I try to be first to bottom bush, where I will wait for enemy champions to approach once they get close I will 'Decoy' out and hopefully they will waste spells and summoner abilities, if my team is on the ball and in the bush behind, they will come out and pick up a kill or two.
If we decide to gank their solo in jungle or counter-gank their jungle gank :P I take 'Crushing Blow' because the damage is very helpful and if my team targets the champ I hit we can take them down extremely quickly.

Over-all WuKong is a very sneaky and exciting champ to play and will cause much frustration to your enemy when they realize they started their combo on your clone and you are in their face wacking them!
Personally most teams I join are reluctant to let me solo (most people have has bad WuKong team mate) but they are pleasantly surprised when I start getting kills (and not feeding) but also setting up kills for them with my ultimate

A few fun things to do are, when an enemy is close but knows they can't engage use your joke WuKong will then raise his staff high in the air and make jokes about them!
Another fun thing to do is, if you are close to destroying their Nexus just before it is destroyed if your ultimate is up, use it WuKong will then spin for an infinite amount of time on the Victory Screen (also works for if your defeated :C)