I play on NA servers under the name JustaBaka, I am a competent and adaptable player, this guide works perfectly for my style of play. First build is a pure support and the second is offensive support, if you find either guide helpful give me a vote, enjoy.

Lore

Soraka, the Starchild of Ionia, was the first of her kind. While there are many who tap into the rich magical energies of Valoran, she was the first to tap into the magic of the cosmos itself - the celestial sea in which it is theorized that Runeterra swims among other like bodies. While Runeterran magicians are limited by the finite (though tremendous) powers of runes, there have always been those who have searched to go further. Reaching beyond the terrestrial firmament of Runeterra, Soraka was capable of invoking the power of the stars, evolving beyond her kin. This power has changed her in fantastical ways - it is for this reason that she became known as the Starchild.

Though Soraka was once trans-human, Soraka has fallen since she let the most primal of emotions rule her. Warwick, a mercenary chemist in the service of Noxus, had caused untold suffering and death among Soraka's people. An alchemical genius who took no responsibility for the atrocities he'd caused, Warwick became known as ''the Deathmaker'' by the Ionian people. As Noxian murder and terror pushed ever-forward across her land, unstoppable anger and hatred welled within Soraka. She called down the power of the heavens to curse and forever change the Deathmaker, and she mutated the man into a werewolf - a wild, murderous beast. For this misstep, Soraka lost much of her power, sacrificing her trans-human ascension and sliding several steps down the evolutionary ladder in an instant. Though she is still a champion of the Ionian people, Soraka has joined the League of Legends in hopes of reversing her curse and redeeming herself in the eyes of the stars.

Though having fallen from grace, Soraka is nonetheless determined to once again be one with the stars.

+Map control with warding + Clairvoyance
+Sustainability for you team in fights and pushing
+More survivability compared to squishier supports
+Easy to learn

-Looooooooong cooldowns
-Hard to contribute if your team is lacking
-Easily shutdown without proper positioning

Greater Mark of Armor These marks are better if you're facing a heavy AD team.
Greater Mark of Ability Power Also a viable choice if you feel your heals need a boost.

In my opinion seals and glyphs should stay the same, not dieing and healing before someone else dies tends to be helpful.

Greater Quintessence of Armor Should be more than enough to help with lane sustainability.
Greater Quintessence of Magic Resist More magic resist if you feel you'll need it, not recommended but viable.

Survivability and damage masteries are not required, nor is a full support tree. Cooldown reduction is imperative to your cause, Soraka's cooldowns are atrocious. You should not have mana problems unless you teamfight several times in a row, regardless you don't need extra mana or mana regen. Soraka's mastery tree can be changed around as you like, with cooldown Quintessences and Glyphs you can reach the cdr cap easily.

Summoner's Insight for flash and clairvoyance buff.
Skip Runic Affinity with Infuse you should not need mana, give it to your AP teammates.
Intelligence to help reach cooldown cap.
Swiftness to help with your movement speed if you can't rush your boots quick enough.
Greed + Wealth to help with overall income, you're job is to ward this will help you do so.
Awareness + Sage Faster leveling means better heals, since you might be running back and fourth assisting any teammates that need it your leveling can suffer, this prevents that.
Mastermind more summoner spell usage, supports need this skill.
Hardiness and Resistance for extra armor/magic resistance respectively.

Basic spells, flash to escape or get off a heal/silence. Clairvoyance for map control.

Extra healing will result in a won early fight, use this if you're unsure of your team but sure of your escape abilities.

No other summoner spell combinations should be used for a purely support champion, you need clairvoyance always. Exhaust or Ignite should be left to the rest of your team to pick up. Again we do not need mana Clarity is out of the question.

Astral Blessing Level this first! With 10 second + cooldowns we need those heals to count.
Infuse No mana cost to restore mana to yourself and an ally, level it second.
Wish Game changer, put a level in this when possible.
Starcall Not here to deal damage, level it last.

W first, E after, R when you can, Q last to simplify it for you.

We focus on Astral Blessing first because of the long period between each use. You'll likely be against an AD carry so the armor buff will also help your teammate trade with him. Generally you'll be able to outlast any combo other than Sona + whoever! If you're bottom lane if facing heavy pressure don't be afraid to help harass, do not overextend or put you or your teammate in a bad position. Infuse is next to keep yourself topped off on mana and provide silence/harass. If you happen to be laning with an ability power champion be sure to level Starcall earlier than usual, the magic resist buff will help tremendously with your harass. Don't be afraid to harass with Infuse it has a long range and will also prevent skill harass with its silence. Always use your Wish sooner than later, generally a teammate will run when his health gets low, possibly dieing or not getting you an assist...I mean picking up the kill. Use wish as soon as you see someone needs it, try to save it for teamfights.

Basic Items for almost every game -
Starting item helps your sustainability, rush it into a Philosopher's Stone as quickly as possible.
You need the extra cooldowns, have I stressed that enough?
You will always have gold for wards.
Not the greatest item, helps you and your team which is all that matters.
More health and just enough cooldown reduction to get you capped.
Extra mana regeneration with cooldown and MPR bonuses to your teammates as well.
Pretty doubtful you ever make it to this item, make sure to build this absolutely last. Be sure to use its active!

Sight Ward Always buy lots of these, try to convince your team to buy at least one per lane.
Vision Ward Counters invisibility champs like Twitch, try to drop one in mid and your lane at the very least.
Oracle's Elixir Mandatory in most games, make sure to be safe when searching don't facecheck bushes you're unsure of.

Now you may find this build ridiculous since it includes no AP to boost your Astral Blessing. Soraka has more than enough heal with no AP, also focusing on items like Aegis of the Legion helps your entire team all the time. Effectively reducing your need to get off gigantic Astral Blessings repeatedly.

This will counter AD heavy teams while assisting your mana pool, active is also pretty helpful if used correctly.
More magic resistance for you and less for them, especially helpful with a fed AP teammate. Also gives a decent boost to your Ability power.
If you're getting murdered by stuns/cc this will save your life.
Elesia's Miracle If you need a bit more tenacity with or without the sash this should keep you covered, no big item purchases need to be changed either.
If you aren't reaching your cdr cap quick enough you can pick one of these up to take pressure off your lane.

Ward your sidebush and regular bushes if you feel it necessary.
Keep your teammate healed and give them mana, some players need to be reminded to spam skills.
Harass with your auto attacks and Infuse, keeping your mana up is more important.
Keep watch for teammates that need Wish, don't ignore your own lane or check while you are out in the open.
If no one calls for a Clairvoyance spam it nonstop, general areas are unwarded lanes/dragon buff or blue buff if teammates are in position to gank it.
Since you will generally be bot lane try and keep dragon control with a Vision Ward, simply run over and kill the enemy team's Sight Ward when they place it.

Main points you need to focus/improve on

• Positioning
• Map awareness for Wish
• Warding effectively
• Most valuable healing/silencing targets

Teamfights -
Stay behind your team! Never engage first unless you need a clutch silence.
Healing priority goes to your carries, no exceptions unless they will live regardless of who you heal.

Wards
River and jungle entrances need to be warded at all times. Dragon and Baron need to stay warded as well, bushes are necessary but take second priority to river wards. Keen map awareness will keep you safe as long as river is warded. Anytime you shop buy at least one ward.

Heal/Silence
Keep your carries alive, if there is no serious threat to silence give mana to your AP damage champions.

Learning to ward and position yourself correctly in teamfights will win you games, plain and simple. Wish can and will change the tide of a game in teamfights or any other engagements. Make sure you do not take any creeps from your lane partner, they need it far more than you and your gold per 5 items will sustain your income. And finally have fun, its discouraging to have an incompetent or bad team that prevents you from winning. But staying positive and focusing on bettering your own gameplay will pay off.

Despite others claiming high deaths are fine, they are simply avoidable and idiotic to have. With proper placement and intelligent use of Wish + Astral Blessing you should generally have three or less deaths per game.