This is my personal build for soraka...
I played many matches with her, and i daresay, this build is very forgiving, and also very "Disruptive".

By disruptive i mean the enemy team will want to focus you, coz you are soraka, and thats what people do (you might have to persuade them a bit by playing "tanky" -> pretending to run out of range of your team, silencing the ap carry so the enemy team will want to attack you and so forth) But since you have (still) good heals and are so tanky they will not get you down, or take long enough for your team to take them down instead.

I advise (or atleast kindly request) that you try it before downvoting, i'm not saying its the best soraka build out there, but its very forgiving for new soraka players.
You will need practice if you are completely new to soraka.

and last but not least, play balsy even early game, you want ppl to think you are bad, or overconfident, or just a pain in the *** silence spamming **** :)

*ps first guide, up for hints and tips and stuff

I go for armor marks since you are the bot support and in the current meta that usually means ad adversairies

Gold / 5 seals and quints will give you 5.3g/5 + masteries = 7.3g/5 + you should really get some kills if you know the person you are playing with.

cdr glyphs, because more heals + more mana spamming (this is changeable with mr/armor/ anything else you might want) but with these runes + masteries + items you get 40ish cdr

These items are not carved in stone, if you are facing a tryndamere + ashe + fiora you'll want to be getting thornmail in stead of frozen armor (get your offtank or real tank to get frozen then)

or perhaps they are not so wild on ad you can toss in a force of nature in stead of a frozen heart.
You should go with the flow, however, do try to get a high cdr and atleast 100 of each mr/armor

Again this skill sequence is subject to change on the moment at hand. For example for some reason you lane with morde bot, or any champ without mana, you may want to take more ranks of heal first. However do not underestimate the silence on E. It is very handy to support your lanemate (silencing trist so she cant jump/flash away is priceless) and it will make you a more likely target endgame, because ppl will find you annoying.

You should explain your team that you want to be the focus of the fight, since ppl will tend to flame you for "risking your life"... Explain them they need not to worry but instead unload everything they got on the designated target.

+ PRO
+ Excellent "initiator' (she lacks skills to do so, but you just facecheck teams and that'll do)
+ very forgiving
+ you can be a real pain in the *** with silence
+ still a mana battery + healer early game
+ average early game → strong mid → godly with full build
+ spot for another dps since you can actually tank (being soraka is usually enough cc/disrupt/reason to be the target of nme)
+ Endgame spamming Q will reduce mr of enemy team by 120

- CON
- Not as strong heals as usual
- 90% Of the times ppl will flame you if you lose ( it still happens, you cannot win every game in your life)
- 90% of the ppl will whine coz you buy GA
- warding is not as easy as it should be (atleast not for me, but thats probably my own fault :)
- no dmg whatsoever