This guide will teach you go to play and master the way of carry soraka.
First of all be ready to be flamed if you fail this, since she is widly known as a support and not carry people will not go easy on you if you fail, but that just makes it better when you show it in their faces how good she can be.

For runes I go red Spell penetration and rest ability power, or red and quintence spell penetration if that works our better for you.
I like to go for abit more AP from my runes since Stallcall brings most of the spell penetration you will need to take the enemies down.

The items you choose it highly situational regarding if you dominate your lane and having the push you might wanna go for a Tear of goddess and make that into a Archangel's staff but if you are having trouble on your lane and are very pushed back, you might wanna go for a Catalyst of the protector which you later on make into a rod of ages.
I put what I usually build the archangel's staff since I usually have the push onto the tower and have the tower killed unless I meet a very skilled played.
Thats early game, and mid/late game its pretty much as for all champions that you go for what fits the game for example you do wanna go for a Zhonya's hourglass or Rylai's crystal scepter if you are focused alot, and if you aren't you might wanna go for a early rabadon(which you always should buy but many times you might wanna go for a survival item before it since many times you are their main focus if you played carry soraka right)

Here comes abit tricky part where you gotta read the game abit more.
If you meet a aggressive player you might wanna go for earlier points in Infuse to silence them and make you harass way better.
If you meet a harasing player you do wanna go for atleast 1 point in Astral Blessing early so you don't have to leave the lane too much, but most of the time you only need to put a point here once maybe twice and then harass back which most of the time is enough.
If you meet a passive player go full out Starcall and Infuse for the maximum push on their tower(this is the thing you want) with early starcall points you easily takes down your creep waves and are able to put pressure on their tower and take it down early, I've been able to push down a tower at lvl 4 with my Starcall pushes.
If you meet a passive player with a jungeler often trying to gank you might wanna go for a Infuse with abit more into astral blessing (but remember you are carry don't leave all dmg behind) when you hit lvl 6 you will almost be impossible to gank if you play your cards right and don't tower dive unecessary.

For summoner spells I mostly go with Ignite and Flash.
I do feel that you can replace Ignite with whatever you feel better to use but curretly flash is way too good to replace.

Pros:
+Probably the best lane pusher there is out there in early lvls.
+Very hard to gank after ulti time.
+Stable dmg that won't fail becuse of 1 Banshee's viel.
+Starcall works great with other AP champs.
+Heals for 600-800 late game with an AP build.

Cons:
-Abit on the weak side late game.
-Got no real burst damage.
-Got no escape ability so easy target in team fights.

This is my guide on how to play carry soraka, it might not be the best but its how I play her and for me it works out great.

The guide is not yet finnished so leave your comments on what you think about this and what I can make better/clearer.
And remember to vote.