I present to you cooldown reduction (CDR) thresh. The core of this build is the 5% CDR in masteries, the 15% CDR 'Lucidity' boots, and the 20% CDR in Talisman of Ascension. This 40% CDR will give you a 3 second cooldown after a hook lands and tugs. This makes peeling for your carry easy and your champion even more of a pain for the enemy team than ever before.

Early Game/Lane
In order to climb in the support role you have to know how to play with every type of ADC. This is, if you aren't duo queueing with an ADC. Some ADCs are hyper-agressive, others are farmers, and none of them are on the same page as you. In lane I like to stay passive until told to attack. This is even more true because of the weakness of this build early game. Because you haven't built any health or resistances until your first back, you can't afford to lose an engage as it will likely result in you or your ADC's death. Soul Gathering is also important to be successful in the mid game. You don't have to walk all the way up to the soul to gather it so don't if you are in a passive lane. Also make sure to take as little poke as possible when collecting souls or it could mean your death.

Mid Game/ Roam
Once towers start to fall but your team hasn't exactly grouped yet you need to keep a few things in mind. This stage of the game is where the most catching occurs, make sure you are with a teammate whenever you are roaming through blind territory. Be sure that you always have wards down at key places. Always have dragon pit warded (if you can get to it). If your team lost the early game make sure to have your own jungle warded, especially the bottom side buff. If you won early you may want to try to get their bottom side buff warded, but make sure to keep safe in the process.

Late Game/ Teamfights
One word. Peel. That's your entire job in the late game.

I pick exhaust because AD carries are taking heal in this patch and the double heal doesn't work as well. With that ignite isn't a great pick because the enemy ADC will likely have heal.

Start
The item start here is based on not exchanging too much early and just waiting for your opportunity to first back. That doesn't mean you have to back off from every exchange however. Make sure you remember your lack of defense.
First Back
Your first back grab the sight stone most importantly if you cannot afford anything else. You cannot afford the sight stone, grab Nomad's Medallion and a ward. In either case, you should get back to base as soon as you can afford the other.
Core
Get these early, they become most useful at level 9 when you have maxed your hook and you have the 3 second cooldown I talked about earlier.
Other
These are very important to build situationally. If your ADC is taking a lot of CC or they have heavy AP, be sure to pick up the Mikeal's Crucible. If your facing heavy AD, grab randuin's.