Guide is in progress. I write for fun. PM if you like.

Ah support, that dreaded last-pick role where you are completely at the mercy of your team.

I used to think any champion can support, and I still do - when bot lane happens to win, that is. But when you're not winning, playing a non-support champion renders you useless and the game sucks to play. So, to not dread playing support, you want a champion both that you find fun and that can survive a losing lane and be useful having nothing but a t1 support item and a sightstone.

Lots of support champions have awesome things about them that make them fun to play to some people. But for me, I have fun playing soraka. Fun parts are:

1. Healing people that are about to die is troll as ****.
2. The mechanic of losing your own health to heal people and gaining it back with your skillshot is engaging.
3. You have good cc to go toe-to-toe with anyone on the other team - a slow from the center of starfall and an instant aoe silence and delayed aoe root.

This really applies to any support role. Good supports don't be *******, they get in the fight, they harass, they secure kills, they facecheck to ward, and they die valiently - tank or not. And soraka is no exception.

As soraka you are very squishy, especially early game. My first games as soraka I fed like mad, you die when people blow on you; one skillshot that hits can end you. You're going to have to get a feel for what you can get away with. But that's no excuse to play like a *****.

Here's a list of full-ham soraka plays you should be making:

1. Harass the opponent bot laners.
Use your auto-attacks at every opportunity. They do significant damage early and even late game in a close fight. They also give you +3 gold from your support mastery. However, care as to the meaning of "opportunity" - you don't want to take minion aggro, and you don't want to expose yourself to an all-in spell like a hook, a leona stun, a leona flash stun (that one hurt the first few times I saw it), a morgana binding, an urgot slow. In an all-in fight bot lane auto-attack the whole time, including when chasing a low enemy or retreating from a low enemy - just care for when their hook comes off cooldown and they turn on you. Harass is key for keeping pressure off your adc; simply healing them is not enough.

2. Defend towers with your LIFE
Towers are a BIG deal throughout the game. Losing a T1 tower early in the game ****s that laner, and losing the T1 bot tower means saying goodbye to your adc farming, to every dragon, and to midlane because bot will roam to mid too. In the mid-game T1 towers aren't worth it but a T2 tower is. I would defend a T2 tower to the death against up to 2 people; more than that just retreat because they will get it for free anyway. Finally, T3 towers are obviously a big deal, but if your team got aced and they are clearly going to get it whether you die or not, just let them have inhib and defend the nexus. On the other hand, don't try to defend inhibs, you can't fight people straight up.

3. WISH - Save until someone is below 40%, then use it - either on yourself, your ally, or a fight across the map.
Wish has 50% increased power on someone below 40% so you want to use it below that mark. However don't try to be cute and save it until they are just about to die - many a time I've tried to do this only to be surprised in how a single spell kills my key squishy from 30% health to zero. Also removes grievous wounds, including from ignite (does not remove the dot).

4. Get in assassin's faces
If you see an assassin, do NOT run scared, get on top of their case and stay there. Fed zed, kat, kha, lb, di, irelia, jax, riven, shaco, rengar; you are the assassin's worst nightmare with wards, with oracle's, with keeping vision on them, with your exhaust, and with your all-important INSTANT-CAST AOE SILENCE. Keep vision on the assassin when feasible, zone them. DON'T waste your exhaust or long-cooldown silence; keep them ready. If the assassin uses their ability to jump on you or your carry or your tower, silence exhaust oracle's starfall auto heal wish mikal's GG. You should actually be much more scared of tanks because they can kill you easier than an assassin - stay away from tanks.

5. Heal until 1 hp and stay in the fight until your whole team is dead.
If anyone on your team is dying, you had better be dying too. Run up and heal them, starfall to heal yourself, and heal them again until you are 1hp. Just be sure to dodge the jinx ult and not get close to tank. The troll possible when a katarina jumps into the middle of their entire team and is focused by all of them but gets a heal, a wish, and a mikaels and doesn't die is epic, but you'd be surprised at the damage anyone can put out when you effectively double their hp. However this applies to fights only; during the poking/positioning phase before a fight you should moderate your heals to balance your allies and your own health.

In any lane recalling is a big deal. It puts you behind, your enemy ahead, and can even cost your tower. In bot lane the stakes are twice as high. Staying in lane consists of managing your health and your mana. This section will take a mathematical look at maximizing your health regeneration with the aim of not recalling before hitting level 6. The idea being with reasonable mana management on the part of you and your adc; if you regen enough health to stay safe and alive and to heal your adc to the same levels you'll have better bot-lane performance.

Equation 1: How many waves do you need to stay in lane to hit 6?
* Experience to level up: 280 + 380 + 480 + 580 + 680 = 2400
* Experience to level up 2 people: 2400 * 2 / 1.1 =~ 4400
* Experience per wave: 59 * 3 + 29 * 3 + 92 / 3 =~ 300
* Waves to Stay in Lane = 4400 / 300 =~ 15 WAVES

Equation 2: How much health can you regenerate in a wave?
HP/s or HP/5 is kind of hard to feel the significance of, so looking at things in terms of HP/wave can give you a better sense of its impact and on a timescale that makes more sense in terms of what kinds of trades you expect to happen per wave.

A wave is 60 seconds so one needs simply multiply HP/5 by 6.

19 hp / wave : Base Health Regeneration
2.5 - 4.0 levels 1-5: average 3.25

12 hp / wave : Recovery II
2

8 hp / wave : Strength of Spirit
351 - 536 mana levels 1-5: 440 average * .003 = 1.3

5 hp / wave : Vampirism III
you might reasonably expect 3 autos and one Starcall hit per wave
auto = ~54 dmg * .75 after armor; 3% of 120 dmg is 4 health regained
starfall = 70 dmg * .75 after mr; 1/3 for aoe: 1% of 53 dmg is 1 health regained

10 hp / wave : Perseverance III
assume 75% health as a reasonable safe value and 644 health at level 3 = 161 missing health = 1.6

30 hp / wave : Ancient Coin Passive
5 health for near an enemy minion death

30 hp / wave : 9 Greater Seal of Health Regeneration
.56 (5/9) * 9 = 5

18 hp / wave : 9 Greater Seal of Scaling Health Regeneration
.11 (1/9) * 9 * level 3 = 3

15 hp / wave : 9 Greater Seal of Armor
9 armor is 9% damage reduction at 0 armor, and about .75 * 9% damage reduction at 30 armor = 7% damage reduction; assume 3 autos at 70 damage per wave = 210 damage * 7% = 15 damage blocked

10 hp / wave : 1 Health Potion
A pot heals 150 hp but you want to stay in lane for 15 waves.

16 hp / wave : leveling up
Your base health goes from 529 at level 1 to 770 at level 5, a gain of 241 for 15 waves.

31 hp / wave : Starcall
Assume 1 Starcall landed per wave at the reasonably-safe level of 75% health. 25 + .4 * 0 heal at +25% effectiveness

8 hp / wave : 3 Quintessence of Ability Power
A starfall has a .4 ap ratio heal, .4 * 15 * 1.25 = 8

6 hp / wave : Block II
Assume you take 3 autos / wave

4 hp / wave : Unyielding
Assume you take 3 autos and 1 spell / wave

Soraka's abilities scale with ability power, but they also have base values, so what percent improvement are you actually getting with ability power purchases on Soraka? For example, if an ability does 17 damage and scales with 100% of AP, that ability has 17 base ability power - if you bought 17 more ability power, you would double the damage of that ability. If the ability instead does 17 damage but scales with 50% of AP, that ability has 34 base ability power - it would take you 34 more ability power to double the damage of the ability. The same concepts apply to buying HP, resistances, AD, and attack speed. It *inversely* applies to CDR.

Note that even though some of Soraka's abilities get bonuses based on perfect hits or missing health, because all these bonuses are percent bonuses they have no effect on the base ability power calculation.

Damage

Soraka's primary job is to heal and the primary purpose of Starcall and Equinox are to heal her or their crowd control effects. However they also deal damage and can help turn even or near-even trades into advantageous ones or even wave clear. But as a more visceral example consider that fed LeBlanc jumping on your adc. A fed LeBlanc is likely to have built all damage and be just as squishy as her base stats, about 2000 health and 30 mr for about 2500 effective magic health.

Starcall Damage = 70 / 110 / 150 / 190 / 230 + .35 AP
Equinox Damage = 70 / 110 / 150 / 190 / 230 + .40 AP

With 0 AP, a non-perfect Starcall and non-procced Equinox will chunk LeBlanc for 1/5 of her health. Your ADC may be doing 600 damage but only be able to get off two autos and a spell before LeBlanc can cast her full combo, and your extra poke is what's needed to finish killing her before she kills your adc, no matter how much you heal.

So what difference would Soraka buying AP have on her damage contribution?
Base Ability Power = Base Value / AP Ratio

Starcall Base Ability Power = 200 / 314 / 428 / 543 / 657
Equinox Base Ability Power = 175 / 275 / 375 / 475 / 575

To put these numbers in context, let's assume you've maxed one of these abilities and the other is level 1, and you buy a Rabadon's Deathcap giving you 156 AP. Your maxed ability, with a BAP of about 600, will do 25% more damage. Your level 1 ability, with a BAP of a bit over 156, will do a bit less than double damage.

This sounds pretty lackluster, so I decided to compare with LeBlanc. Sigil of Malice does 155 + .4 AP at max rank (again, the fact that it can be doubled doesn't change the BAP), which gives it a base ability power of 388. A BAP of 400 is 50% less than a BAP of 600, so a Rabadon's Deathcap does make more of a difference to LeBlanc than to Soraka. But the BAP is still higher than I expected - a Rabadon's Deathcap only makes 156 / 400 = 40% more damage on Sigil of Malice instead of something like double.

Healing

On to Soraka's primary job.

Astral Infusion Self Heal from Starcall = 25 / 35 / 45 / 55 / 65 + .40 AP
Astral Infusion Ally Heal = 120 / 150 / 180 / 210 / 240 + .60 AP
Wish Heal = 150 / 250 / 350 + .55 AP

Repeating the base ability power calculation.

Astral Infusion Self BAP = 63 / 88 / 113 / 138 / 163
Astral Infusion Ally BAP = 200 / 250 / 300 / 350 / 400
Wish BAP = 273 / 455 / 636

Bonus from Rabadon's Deathcap at max rank:

Astral Infusion Self = ~100%
Astral Infusion Ally = ~40%
Wish = ~25%

Here's where things get more interesting. AP on Wish is again only marginally effective. But AP on healing allies with Astral Infusion is the same effectiveness as on LeBlanc's Sigil of Malice, and the effectiveness on self-healing from landing Starcall is astoundingly doubled! So is buying AP worth it? To answer that, will have to examine the competitors to AP in fulfilling each spell's job.

One unique thing about playing Soraka is that even as a support you feel like playing a damage carry like an adc or a rapid-fire mage like Cassiopeia or Karthus. Astral Infusion has a 2 second cooldown at max rank, and that's 1.2 seconds at max cdr; and you more or less spam it throughout the entire fight intermixed with other spells and actives; the only difference is you spam it on allies instead of enemies to maximize HPS instead of DPS.

In this section will look at maximizing HPS using only chain-casting of Astral Infusion as a trade-off between buying AP and buying CDR.

	You Have 0% CDR	You Have 10% CDR	You Have 20% CDR	You Have 30% CDR
You Buy 10% CDR	Or You Buy 44 AP	Or You Buy 50 AP	Or You Buy 57 AP	Or You Buy 67 AP
You Buy 20% CDR	Or You Buy 100 AP	Or You Buy 114 AP	Or You Buy 133 AP
You Buy 30% CDR	Or You Buy 172 AP	Or You Buy 200 AP
You Buy 40% CDR	Or You Buy 267 AP

So 10% CDR is equivalent to 44-67 AP depending on how much you have already. Now let's examine some sources of 10% CDR and about this much AP.

Forbidden Idol = 600 gold