This is a basic outline for the new TT Beta. The emphasis is being tanky(Which is needed in 3v3) but also being able to carry. The main item in this build is the Atmas; this stacked with HP makes you ridiculous. With this build you'll be able to withstand damage while dishing it out.
The only items that should never change in every game are the boots of swiftness, Overlords bloodmail, frozen mallet, and Atmas. The other items are situational. If they have AP build a Maw...if not then you could either build more armor/HP(Sunfire) or more damage depending on how much you're getting focused. The IE is one hell of an item...your spin to win crits! This makes you chop everyone down the only con to this item is other than damage and crit it doesn't provide you with any more survivability so you need to make sure you can afford the trade-off.
The correct runes are a must! You can play with the masteriest slightly if you'd like but I suggest going tank masteries. If you have the correct runes you'll be naturally tanky from the start.
I could possibly add a gameplay section here later on when I have the time; but for now enjoy the build.