Greetings Urgot fanatic! I have for you here a balanced Urgot item build that deals a surprisingly large amount of damage and still manages to keep you save from all sides with a well proportioned amount of Magic Resist and Armor.

You're gonna want to start with a Meki Pendant and 2x Health Potion to start with building your Tear of the Goddess which you will get on your first Recall.

On your second Recall get your Boots and Manamune. Now you can start dishing out some damage. Get a Sheen to really get something going.

After a while you will have enough money to get your Mercury's Treads and a Phage which you eventually build into a Trinity Force. Now you got your main damage sorted you can start working on your Banshee's Veil working your way up with a Negatron Cloak first to keep the AP nuke's from doing too much damage.

Now you have your Banshee's Veil you can start building your fifth item.

Recommended:
Frozen Heart - Take this item to complete your defensive item build. This item is great because of the Armor, Mana (extra AD), CDR and Attack Speed reduction aura. Best pick by far if you don't have a fed Attack Speed champion batting you.

Situational:
Thornmail - If you have any Attack Speed champion dishing out some heavy damage, take this.
Bloodthirster - You are managing really well in team fights and don't feel the need for more defensive stats yet. If this is not the case, get this item last.

My Summoner Spell picks are very simple:

Flash - Simply a great spell to get in or out of a fight. WILL save your butt more than twice!
Exhaust - Urgot can be squishy and with his HYPER-KINETIC POSITION REVERSE he will often end up on the enemy side of the fight leaving you open for easy focussing. Luckily your build helps your fight this and Exhaust is a great addition to this build.

Optional:
Teleport - If you are going mid lane and want maximum lane presence, take this. I normally don't find myself needing this spell as it is not a hard thing to dominate your lane with Urgot. You can simply force your opponent to leave or kill him/her and Recall afterwards.
Ignite - Good to counter supports and get First Bloods but, personally, I would never pick this on Urgot since I rely on my long ranged harass where my ignite won't reach. I would rather have a team mate take this item to combat those pesky supports.
Clarity - If you're not so experienced with Urgot yet this could be an "ok" pick but it is not recommended. Later on in mid game you won't find the use for this item as you will have your Manamune ready to supply you with plenty of mana.

You're going to want to start with Noxian Corrossive Charge simply because of it's range. Somehow it scares people and it will prevent them from getting early minion kills.

Once you hit level 2 you start maxing out your Acid Hunter but be sure to get at least one rank of Terror Capacitor for the slow and the shield. Terror Capacitor will also be the second skill you max out. It's shield is more than worthy and the slow is just wonderful when you have people running away or chasing you.

The reason you max out Noxian Corrossive Charge last is because it's damage is simply too low for it to be worthy of spending your points in before maxing out the others. Sure, the DoT is handy for people that almost died but got away but your Acid Hunter is more than capable of taking care of these people.