Of all the characters in League of Legends, Soraka has to be my favorite. A bit of background about me as a player and why Soraka in my opinions is one of the better supports available in the game. I own every single support in the game save for 1 or 2. I play others often and I am a big fan of Karma and Sona, but I just really enjoy Soraka the most.
I'm a healer by nature. I've played countless online games since around '97 and have been healing in all of them. While I do enjoy healing, I enjoy playing characters which can easily with a little bit of spec change can be powerful offensively. Soraka is that kind of healer, one which you can play very supporty and get games where you have 7/12/31 style games or you can go pretty offensive with her and end up with a 24/4/8 style game. I always like to end games like that were I'm playing aggressive AP Soraka with the quote "I'm Soraka, and I'm a support". If you get to enjoy playing Soraka, I highly recommend the Divine skin. Personally I can't stand the unicorn business.
Here is my average night when I'm not playing with complete idiots. The one defeat of the night I was laning with a terrible Teemo who spent more time badmouthing the team than actually playing.
Here is a livestream of that night @ Twitch.Tv/Livistos
This guide is purposefully not a mile long like a lot of these guides on this website. You won't find a million images or guides on how to place wards. If you want a guide on that junk go search elsewhere. I believe in giving your the best wisdom I can offer in the shortest amount of words. I'm not in a competition on how long my guide is vs others. In each section I will break things down from a support and then agressive perspective.
Well, onto the rest of the guide.
I picked these runes for two reasons. First, I wanted one rune page which would work well for either support or aggressive Soraka. Second, while I think Quiessences and Marks are good for early game, I generally prefer Seals and Glyphs to scale with level to give a better late game bonus. Really the runes are the least important part of this build. If you feel you need more health, swap out the quiescence. If you need more cooldown reduction, go that road. Those are minor comfort level adjustments.
One advantage of using a rune page that works well for either of these builds and masteries which are close enough to one another ( see next section ) is that if you go into a game expecting to play one way but then find the need to switch to the other build you can easily with just buying the different items. I've often found in solo play that you go into a game intending on supporting, your carry either sucks or disconnects and then you have to go aggressive to stay in the game. I've done that and turned the game around several times.
The masteries I chose are pretty much what most people go with for a support style character. You will be buying glyphs a lot so getting that extra gold is nice at the onset of the game. Support Soraka prefers utility ( of course ) and a little bit of defense while aggressive Soraka still prefers utility over offense. I have played around in the past with going 21/0/9 with an aggressive Soraka, but she's still a support and you can't go full offensive with her because you just won't do well.
Note that in both support and aggressive Soraka mastery builds, I do get get the extended range on the wards, again because I think even if you are being aggressive, you will be ( or should be ) buying wards more than the other morons on your team.
When playing support Soraka, the skill sequence is simple. Your priority is your heal, then your infuse, then finish off your star call in the later levels. Especially in early levels before you have a lot of items, getting those heals early is huge. Soraka's heal doesn't scale well with items so just getting the levels is enough for the early to mid-game and then cooldown reduction makes it so you can drop those heals more often in late game.
When playing aggressive Soraka, the skill sequence is opposite. Your priority is your star call, then your infuse ( because the silence and spike damage is boss ), then finish off your heal in the later levels. By the time you reach level 5, expect that level 3 star call to quickly be doing unexpected levels of damage to your opponents.
Work in progress...
My item builds are similar to some other people's but I've made very important changes to my build order in favor of some key things. Details on my picks later.
When playing support Soraka, your goal is to healing / infuse and generally support your carry on bottom lane. Soraka lanes on bottom well with a ranged AD carry who has a mana bar. Ashe, Cait, Trist, and Graves are excellent laning partners for Soraka. Remember that as a support, you're doing your job if he lane is warded, your carry has full mana and health, and you don't have more than 10 creep kills by level 15. Keep using your heal on cooldown and infuse to either give your lane partner mana or to harass the opponent.
When playing aggressive Soraka, your need to act like an AP carry though you are still best laning with somone on bottom, preferably a tanky AP character or an assassin. Some melee who wants farm, but doesn't need it. Be polite and don't hog all the creeps and don't overpush the lane either. Starcall makes it easy for you to accidently over push, but at the same time it makes farming super easy. As aggressive Soraka, your goal is to constantly be in a place of harrassment. Piss off the opposing team with your silence and a starcall or two, then back off. Push them back in the lane so your melee lane partner can share in some creep farm. Again, there is a tough balance of not pushing too much though.
General strategy on skill usage whether supporting or aggressive, silence big bomb AP or control champions, spam star call, remember you can ALT+W to self heal ( because you often will be focus fired ), and if you aren't being FF'ed then keep your top dps alive. Being able to target enemy champs to silence or friendly players to heal them in the key of battle is something you will have to perfect over time. It's very fast paced and you almost have to have a bit of what I always call "healing ESP" and know who is going to need the heal before they even need it.
Sorka's ult is by far the most powerful healing ults in the game. This ult really teaches you how to be map aware. Being able to be aware of your own lane, but also when other lanes are having fights is a key skill you need to develop. If around level 6-11'ish you see that there is a team fight at mid or top and you're in bottom lane with your carry, you can pop a Wish to help turn the table on that team fight. Knowing when it's hopeless and not wasting your wish is also something to learn.
When in late game, don't pop your wish too early, stay back and after you see your whole team has taken some damage, then pop your wish. While it might be tempting to use your wish to save the first person who get's focus fired, it is better to heal the whole team for more than waste it healing one person. If the opposing team is really good at focus firing, then you might have to use your wish in this manner. If they are smart they will avoid spreading out damage ( A. because it's dumb and b. because it's especially dumb vs Sorka ).