This is my first quick little build. If you are looking to learn how to play your character, this is not where to look. I am simply making this to get right to the point if you are just starting a game and looking for a quick build.
With this build i have been able to take on 3 people at once and still come out successful at times, and almost always winning when it comes to 2v1 situations.

Please Don't Hate :)

At the moment i am only level 14 and have not looked at the runes a whole lot, but this is what looked to be satisfying. The Magic Penetration will help with all of your skills, along with the important poison you abuse in this guide. The health runes will just help you look meaner, and survivability!

I find this a fairly simple build favoring Cleanse and Exhaust. I choose this because it allows you to still have a tank perspective and take hits while still having a bit of damage in there. change this as you see fit to your play style!

This is the main reason i made this little build
-I start out with the sapphire crystal, like most.
- I then go on to get the Mercur'y Treads for some resistance and CC durations decreased.
- I get the Catalyst of the Protector next, for the health and a bit more mana, and for working up to the Rod of Ages
-Next is where i differ from most builds, i work to getting the sunfire cape. It may not look too appealing, but that with the Poison Trail skill adds up to a lot of damage for just "standing around"!
-The Rod of Ages comes up next, which looks like it was made for this character! With full stacks it gives us about 991 health (due to our passive with mana), 725 mana, and 80 AP.
-Next i usually go after Warmog's armor if i dont notice that AP or AD are killing me, more health is never a bad thing
- This is where things change up a bit. This is where i generally choose between three choices, Banshee's Veil, Thornmail, or Force of Nature.
If you notice there are a lot of AD that you are getting hit with take Thornmail, it will give you even more damage for just standing around and getting hit.
Then you have Force of Nature, if you are getting rocked by AP then you will generally want to get this.
Banshee's Veil, the choice from most builds. I will take this if i still don't notice one really out doing the other,(AP/AD) as it adds even more health, and to negate the one spell every 45 seconds.
For my last item i always want to grab Atma's Impaler. You can be a tank, great, but what happens when it is just down to you and two people from the other team?
The main reason this is such an amazing weapon for tanks is the Passive for it, 2% of you maximum health is added to your damage. So say your health is 5000, which we get close to in this build, that is an extra 100 damage each hit, not to mention the 18% crit and a bit more armor to add

Summoner Spells are fairly versatile, but i prefer to go with Exhaust and Cleanse(or)Ghost
-I choose Exhaust because there is usually one person that gives you troubles, and with this on him he will be cake. Not to mention that it slows
-I choose Cleanse just for when your in trouble and you have been ganked, getting slowed and slowly killed. Cleanse will be able to make it so you can actually get away from this situation if need be.
-Sometimes i choose ghost because if you get stuck in a bad situation like i stated in Cleanse, you still may be able to get out. It is fairly useful if you have a team-mate on the run from someone and you need to get to them NOW in order to save them. Not to mention it can just help you get back into action quicker after going back to heal!

** Remember to change the masteries according to what you chose for Summoner Spells**

So as i said this is a fairly simple build that i just made, it is my first one so please inform me if there is anything i should change/compare to.
You are pretty much just standing next to them and auto attacking most of the time when you get away with it, it sounds bad but standing in the middle of the group you will be able to dish out a lot of damage with your poison!

If there is anything that you think i should change/ i made a mistake with / something that i should mention / etc.. (the list could go on) just let me know!
Thanks for reading! -TairnD