This is only a build, not a guide. Keep that in mind.

I rarely differ from this build no matter what I face. That is why i included only 1 item build.

Mainly it focuses on your Noxian Corrosive Charge+3x Acid Hunter (or 4x Acid Hunter if executed properly) combo with Terror Capacitor active mainly for slow.

Start with Sapphire Crystal for more harras power. just lasthit your minions on lvl 1 with occasional Acid Hunter in tha face if you have a clear shot. Noone should realy exchange shots since you are quite a Acid Hunter spammer and it is extremaly strong early game.
Rush Tear of the Goddess and start stacking it. Next should be Ionian Boots of Lucidity. You dont need to build Manamune as fast as possible. The Brutalizer is enaugh to get damage in early game and inho it is better. Finish Black Cleaver before Manamune. At this point you should have or be close to getting Muramana anyway. You can get Vampiric Scepter before Sheen/ Iceborn Gauntlet but it is only a "minor heal item". That little edge so i prefer going straight for Iceborn Gauntlet.

As soon as you hit lvl 2 (preferably 3) you should already be forcing base teleports or even kills on your lane.

Be aggresive. Dont use Exhaust carelesly if you do push your lane a bit. Save it for Jungler "help" and change a gank into a double kill with ease. Junglers tend to come on 1/2 or 1/3 of their health so it shouldnt be problem to get them down or just run away with Terror Capacitor + Exhaust.

Remember to "tag" both becouse your passive Zaun-Touched Bolt Augmenter plays significant role in mitigating most of the damage. Just run away with random Acid Hunter from your *** to "tag" em and keep on running. If you used Terror Capacitor to shield yourself you will also slow + debuff. Remember that and use it.

Your runes/masteries aremade for maximum Acid Hunter effectivness. Dont waste gold on AS etc. since the white attack will be only a "filler" and Gaunlet trigger.
You should have 39% CDR pretty fast (boots, tbc, gaunlet) + 4% from masteries.

Dont initiate fights teleporting yourself with Hyper-Kinetic Position Reverser into whole enemy team ofc... i hate too see urgots doing that. This is a skill that peals off or CCes in teamight. Not a innitiation tool (ofc can be used like that but its not recomended if you play as a AD Caster role here)
This build is not THAT tanky remember that.
Your ulti catches wondering single enemy champs for execution, or to peal off high value targets in teamfights.

Try to stack your manamune as fast as possible (but dont spam... mana problems are the last problems you want to see in middle of teamfight, no mana = no EWQQQQQQQQQQQ and 0dps since you are made for Acid Hunter spam not white spam.

I know that Iceborn Gauntlet doesnt trigger of Acid Hunter but it is realy handy with the amount of Acid Hunter spam you accualy do. Those white hits will go of "naturaly" and slow down anyway. It also gives some survivability and CDR. It is also great for fast towerpushing. Since your performance drops laster in game you will probably try to split push towers etc, unless fed :D

Many ppl will disagree with the skill order (take Terror Capacitor before Noxian Corrosive Charge bla bla bla) I dont care. I use Terror Capacitor mainly for the slow utility. Play smart and you wont need tons of shield. The lvl 1 slow is enaugh to land required 3 or 4 hunters.
As soon as you get Boots and TBC you CAN (dont have to) call blue for others that might need it more. After getting Muramana and Iceborn Gauntlet you dont need it totaly.

Masteries are set for middle as well. You will usualy get a APC there so i prefer taking Mres flat runes paired with Mres flat in masteries since i want to be as much aggressive as possible in early game focing those base ports and keeping APC from leaving mid for longer and underfarmed/underlvled. Being higher lvl makes you even a bigger monster.. duuuh o_O!

Many skills with urgot has to be "worked out" by yourself. You have to be flexible. Know your "kit" and how to use it.
For me learning the Hyper-Kinetic Position Reverser into Noxian Corrosive Charge combo was the basic burst supprise combo to learn. Everyone should be able to simply execute the Noxian Corrosive Charge -> Terror Capacitor -> 3x Acid Hunter. If you cant.... than learn that on bots. They are pretty good to tech you that. They usualy run away properly and are hard to get all those 3/4 Acid Hunter there. The downside is that you wont learn landing your Noxian Corrosive Charge from bots... they are stationary targets untill getting that Noxian Corrosive Charge in tha face.
So back to Hyper-Kinetic Position Reverser into Noxian Corrosive Charge combo. You have to work out a routine of landing your Noxian Corrosive Charge not on your enemy (especialy not before Hyper-Kinetic Position Reverser! you will waste the dot and time on it) but on yourself (rather the position you were before teleporting). This basic skill will give you pretty nice burst that can be turned into an easy kill even on low hp with execute of Exhaust power... (mastered to lower resistances etc). Remember to land basic attacks on that combo.

More tips and tricks with urgot are kinda... skill based and depend on the game itself. I often amuse myself that i executed that totaly random damage plan... and got double kill off a certain death situation. Learn from those as i did :) It gives you a much needed "feel" of the champion. You will know what you can and cannot do with him.

You dont have any counterpick in my opinion. You should be able to rape basicly anyone. Doesnt matter huge range or burst etc.
Those with bigger range will poke you but if you land even a single Noxian Corrosive Charge, they will get realy realy harrased back. If you get a burster, they should die after executing their combo, since they dont have anything apart that set of skills that now will be on CD and you have nearly unlimited supply of your Acid Hunter damage. You should just dps down those bursters.
Sustain champions can be harder but they shouldnt make your farming hard in that way. They will have to focus on staying on line and staying alive. They will be sometimes unkillable but you should get creep advantage and a friendly jungler will secure those 100% kill situations.