This is my personal build for my friends. With that I want to say that I don't take any critic and I am not gonna change anything in it unless I want to. You can vote if you want to. I don't request that you try it out before doing so neither.

Anyhow, this build is meant for the babysitter supports I main. They work well together with carries like Vayne, Ashe and Kog'maw. Meele carries works extremely well in lane with Alistar or Leona (e.g Gangplank, Tryndamere, Xin-zhao etc) but not too well with Soraka. She needs ranged carries on her lane.

NOTE!!

You should not follow the ability build to heart! Build for what the situation calls for! Are you taking lot of harass? Go in Astral Blessing. Is your carry running out of mana quickly? Build infuse! Also remember, it's important to max Infuse as early as possible too. Especially if the team got a mage like Brand or an initiater like Warwick. The silence is extremely important for your team. The longer the better.

As Soraka, you want to encourage the carry to be able to last hit and harass freely without having to worry too much about the enemy harass. That's why heal is important. And getting mana from infuse won't be much and you need this infuse to restore your carrys mana and protect your carry from harm by silencing. Everything is for the carry, is what a baby sitter should think. Thus Sorakas weakness becomes, ironicly, her mana.

Runes:
To remove this weakness, I take flat mana regen seals. (Strong early regen, and later mana is not a problem anyhow)

Masteries:
As for masteries, I max Meditation and Perservance. Yes even though the last 2 points in Perservance is worse than the first one. Health and mana regen is just godly stats for being durable in lane. And you need to stay there and baby sit until your carry needs to get home.

Pretty much same ideal as above. Alistar is more of an aggresive support though. His cc can easily lead to an easy First blood at level 2. Laning with alistar as a babysitter means heavy offense and great escape potential.
Alistars E-ability should not be considered as a "heal" but rather as an "health regeneration" spell. Don't rely on it to save you or your carry in a fight.
Alistar have a real big problem with mana, so use your spells wisely. Maybe aggressive immediately at level 2, and then wait for regeneration and try out later when your mana looks better. Ideal: You should always have enough mana to spam the heal.

Runes:
To reduce Alistars weakness in mana I recommend going flat mana regeneration seals on him. However, I do also recommend using flat armor seals on him. He is meele after all and when you initiate you don't want to be shot down immediately because if the enemy is smart, they focus the early game squishy alistar when he initiate. This can be deadly if your carry is slow on following up with the initiate. Anyhow, these runes are pretty much equal, unless you're having some weird AP combo at bot which almost never happen in ranked games anyways.
Flat mana seals ~ 4.5 Mana regen
Flat armor seals ~ 10% AD damage reduction
Also, as you want to initiate well on Alistar and perhaps catch up bit by bit and then "stomp'em'up", I usually go with Movement speed quints. They got a huge impact, especially early, and shows their valor even at end game. However, you might just be the more secure type. For you I recommend going flat health quints. You want the enemy to eventually overextend and then do your combo, being much tougher if they intend to take you down. Also it helps you get more durable overall at start. They become a bit useless later on though.
Flat Cooldown glyphs works excellent on Alistar and after these huge nerfes on his ability power scalings they are just primary for Alistar. More abilities from the support, the more supportive he is. Together with masteries it gives a whooping start of 15% reduction.

Can fill this out later as to why she is a godly babysitter for carries. Anyhow there are two builds: One for AD heavy team

(2 carries and a fighter.. perhaps 3 AD. If there are 3 carries just go thornmail and instant win)

And the other builds is for AP heavy team

(2-3 AP. If there is a mage like Brand, Fiddlestick on the team you should really initiate this build. If you get a leblanc on team build a Banshee's veil as quick as possible in mid game).

Jungling path: Blue > Wolfs > Wraiths > Red > Twin golems

Gank: Can gank directly after blue IF good opportunity. Ganking after Red at level 3 usually first blood. At level 4 after twin golems with taunt + red = first blood.

One pot per mob station.

Jungling path: Twin golems > Wraiths > Wolfs > Recall > Blue > Red

Gank: At level 2 try gank mid before wraiths. If you do wraiths you probably won't have the mana. Otherwise gank all the time roam more than jungle.