a little help in building soraka's items plz

soraka is my favorite support champion. her ability to keep all her teammates alive in the fight is really a big changing and turning the tables around. other than the some of recommend items set for her, I see some other items that may be useful. but the thing is, I tried a lot of things but I don't know if they are the most effective. I like to keep my healings high with ability power because I'm better at healing with my W or ulti (+ the ) than using shield or other items on her. here are some items I'm trying on her and can you please tell of they are effective on her :-

to :- I know building this item takes too long but it saved my a lot of times in team fight. I also consider the mana to ability power is strong but something seems off, any thoughts or advice about this item ?

to :- if there is one thing I'm good at, it's running around to stay alive while supporting my teammate to get the kills. this item gives me a lot of AP that helps me in the healings. but dying will make all the effert you putt in the stacks go with the wind :(, so is it really a good item on her or not ?

:- yeah this is in the recommend set, but I personally never saw ... or in better way, never had a visible use of it when I buy it, I just don't understand how useful this after you link to an ally, a little help with it please ?

:- this items helps my to stay alive in battle for a little bet and give a lot of AP, what's the thoughts about it ?

and lastly, a general thing. some items says that it increases a the power of a spell by an amount like and , does that apply on the healing from W ?

if you have a specific build you want to share with me, I'm all open :). my own build is :-