I've never seen a guide that plays like I do, most of them either being for starcall and/or astral blessing. Mine revolves around harassing with infuse and astral blessing.

1: Infuse
2: Astral Blessing
3: Infuse
4: Astral Blessing
5: Infuse
6: Wish
7: Infuse
8: Starcall
9: Infuse (maxed out here)
10: Astral Blessing
11: Wish
12: Astral Blessing
13: Starcall
14; Astral Blessing (maxed out here)
15: Starcall
16: Wish (maxed out here)
17: Starcall
18: Stacall (maxed out here)

Item Build:

Amplifying Tome
Sorcerer's Shoes or Boots of Swiftness
Tear of the Goddess (Do not turn into Archangel's Staff)
Fiendish Codex
Guardian Angel
Stinger
Nashor's Tooth

After that, the game is usually over, but if not go with with Rylai's Crystal Scepter for the slow.

You usually want to go solo, but if you can't, then go with a tank.

I always go for starfall first, then I focus on Infuse and my Ulti, throwing in my points to astral blessing as necessary for regeneration. This greatly ups my pushability and farming power, which I use to harass enemies and whittle away at the opponents tower. I always lane with somebody, but solo Soraka tends to work better if you only grab one level of Astral Blessing so you can harass better and rely on your AP to heal you up.

As for items, I tend to hybrid her as a tank and AP. When done right, her MR reduction really starts hurting your enemies in team fights, and then suddenly you can wipe their entire team.

for items usually it's:

1. doran's + potion
2. Am I getting hurt or have died? If yes, go for spirit visage. If not, I go for the codex for the AP and mana regen.
3. Tear for mana + regen
4. MR resist boots
5. either a rod of ages, rylai's or guardian angel (based on whether or not tanking or team healing/aoe or harass is more important)
6. finish archangel

This is what usually works well for me.

If you aren't getting starfall with a golem buff at level 1, you are completely wasting your time playing soraka.

blessing (to heal person tanking golem)
starfall
infuse
max starfall
max infuse
max heal

Starfall paired with a golem buff makes soraka the most dominant laning hero in the game. Period.
No one can match her staying power, and when paired with another hero, (honestly, any other hero) you will basically almost always get first blood in a random public match. In every game I've ever gotten golem buff at level 1, its always ended the same, first blood, first blood with double kill, setting up first blood, push tower down to death.

You simply have to get innervating lockett as soraka, I'm sorry, you just do.
Also, Sorcerer's shoes? Boots of Swiftness?
Picking up mercury's treads or ninja tabi is absolutely essential.

I see your point, but usually in my games, I harass like crazy with infuse and astral blessing. I usually end up shopping at about 2000-2500 gold, after one or two kills. I also start soloing the golem at around level 6, to give me a boost in my mana.

Innervating locket does not fit my playstyle, the money could be used better (in my opinion).
Also I usually pick up boots of swiftness for the 400 move speed.

I might just try your build next, just to see how it works out.

P.S. My games usually end up in me having 7-10 kills and 0-3 deaths with 7-? assists.