This is my first guide, a strange and not-so-liked one, but realy effective since your goal is to keep your ally alive, and yourself at the same time, and help to takedown enemies.
With this build, healing youself is useless since your ennemies won't focus you for the only good reason that you are tanky.

Pros:
More survavibility.
Less focused by ennemie carry.


Cons:
Less support item.
Lower heal then an ap or support build.

those Greater Mark of Magic Resistand Greather Glyph of Warding help the lack of magic resist you have LATE game, since at the beginning, with your passive, you should easily have over 60. Since Soraka's basic armor at start is only 11, so here the explanation for Greather Seal of Resilience. The Greater Quinteseence of Avarice is a most for any support champion.

Here again, Armor and MR boost from defensive tree with Heal boost, you can take [Flash] boost if you want more mobility, but i prefer using Heal, so be aware of the triple heal in teamfight. Normal Ability Tree. No special comment on

since we need Gper5, philo and HoG gives enough, for boots Mercury's Boots are the top. but if 4 ad with almost no CC, get Ninja Tabi instead, that will make you more tankier. FoN, Frozen Hearth and Banshee Veil are the must in all build. if they have more Ap carry, get Spirit Visage and/or Aegis of the Legion instead of Randuin's Omen and/or Thornmail. Or you can even get Guardian Angel to replace one of those items to get both Armnor and Magic resist. Always try to carry ward to avoid gank.

I maxout Infus]e] and [[Astral Blessing 1st, but, at lvl 10 they must be lvl 4 ech, instead of 5 and 3, it give more sustain in the lane since both are high. at lvl 4 i take Starcall once and max it in last. Like always, get Wish maxed at 6/11/16, because its your best spell to get massive assists and that can save you allies.

i usually take Clairvoyance, and you know why, and Heal to give a triple heal in teamfight that can turn easily the fight in our advantage. You can easily replace [Heal] by Flash to get more mobility, but if you play safely and harass them sometimes WITHOUT ANY RISK AT 1ST GLANCE,you shouldn't need Flash. Cast your CV everytimes it is up, in the enemy jungle or in some bushes to help youself and you allies to kill your enemies.

Well, even if Soraka is build in a Tanky way, she is still a Support, don't EVER play her has a tank, that could be thw worst idea ever made. Since she is a support, the "0Cs" meta is here. GP10 is actually needed for her, Philo stone and HoG combined with masteries and Runes will give her 14Gold per 10 sec.

In teamfight, try to always silence the ap carry or Any massive CC, such like Sona, amumu, etc. Spam your heal on your carry, the +125 Armor at will help them so much, do your Wish and Heal when the enemy team take out there ultimate to save many team mate. Try to don't take any kills if you can avoid it, leave those to the carry, but don't be afraid of getting some if they could escaped.

So finally, a Tanky build for soraka, even without AP or real support build, you do the same job: keeping your allies alive. With all this tankyness, you will never, well more likely, be taken out first. Since this is another "0Cs" Support Meta, GP10 is needed early game to build yourself. Leave the CS to the carry laning with you and try harrassing the enemies and don't be afraid of your enemy, they can't take out soraka that easily.

Any comments to improve this build are welcome. if you don't like it, free to you.