Keep in mind a truely good league player can adapt to situations. This guide is not meant to be an end all meets all. It is to assist with a suggestional build; however subject to change based on your team and enemy team comps

AP Tank Soraka mid/bot lane is a lane bully that after getting her tear has infinite lane sustain and can clear waves of minions possibly even faster than even Anivia. With the slow from Rylaiz kiting chasing players while spamming aoe dmg becomes the ultimate fighting force. Triple kills even pentakills are possible if played correctly. Most importantly dont forget double heal. Soraka's ultimate can also be used to pick up free assist even if you are farming the jungle or other end of the map.

Pros:

Chasing you is a mistake and causes for enemy team wipes.

You can use your Q to see around corners that are usually not visible

You can easily pick up assists even without being in fights and instantly turn the tide of a fight with a heal across the map while still farming.

Good early to mid game while players have less health.

Cons:

High burst gap closers can still cause problems to escaping

late game if players build very high health you will fall off hard

Champions you counter: Virtually any mid mage and non tank champions.

Champions that counter you: Late game any pure tanks that just build tons of health.

I play this build in china server as well as american server
and so far (atleast in china) I have not lost a single game and been first to second in dps.
Most people quit after chasing me and losing 3 players to my Soraka Awesomeness!!! ^.^

Play Video

Make sure when returning to the base the first item you pick up is a Tear of the Goddess. This is to ensure that you gain mana from spamming 2 sec CD starfall. Upon returning pick up your first part of shoes and your catalyst stone to start gaining the benefit from catalyst stone.