Obviously each game will be different, and you likely won't be going against a team with all AD or all AP damage being dealt (if you are, it should be much easier to win; you'd be surprised how many all AD team's you'll fight at low rank play with no tanks).

It's up to you to itemize on the fly based on the opposing teams composition. The items listed above are simply what I deem, and from experience feel are items worth buying on TT.

So lets lay you're fighting a fairly standard team on TT

-Xin
-Nunu
-Vlad

This team comp is pretty vicious, and is pulled from what I deem to be top tier characters on TT (see the amazing post Kings, Titans and Gods of 3s by Adonikam)

http://www.mobafire.com/league-of-legends/build/kings-titans-and-gods-of-3s-85647

You'll probably want to do something like this.

Start with
+1 Boots
x3 Health Pots
-
Merc Treads
Wriggles
Aegis of the Legion
BV
Warden Mail
Hexdrinker
Randuin's Omen

Other items that are of note: Guardian Angel, Force of Nature, oh, and WARD + ORACLE's (for all those Eve, Shaco, Twitch ninja's out there, and to a lesser extent Vayne and Teemo)

I can't stress enough how important wriggles is on this map, especially if you're playing a character like Jarven, who (provided there is at least 1 AD champion on the enemy team) makes incredible use of all that wriggles provides.

Harass with Q and last hit, you should be bottom with an ally, or solo if you have a good jungler. Try and conserve mana for the ganks and team fights so you always have plenty of gas to E buff the team and combo with Q, W can also save your life and insure the kill on enemies.
Don't jump the gun on you're ult, it's probabaly the best initiator in the game, and you don't want to jump into a 3v1 because you were overzealous, especially in low rank games where your team mates will just part like the red sea, watch you die and call you a n00b. You'll simply be left thinking (well, I thought they were right behind me, wtf o_O)

Keeping it brief, but not much else can be said without play testing it.