Hello my name is ChaosTîger.
And welcome to my little and first guide to Fiddlesticks support.
I'm a Diamond player on EU-W who mains support

The reason is why you don't build AP on Fiddlesticks support are:
-You aren't the Jungler
-You neither stay in the front line
-You need Cooldown Reduction,not AP,because your Fear have a 6,6 sec Cooldown with my Core Build
and your fear is 3 years seconds long.So you have 3,3 seconds left to fear the enemy again! Overpowered? Nope a bit a lot Horribly.

Pros

+He got the best hard CC in the game (3seconds fear)
+With 40%Cooldown Reduction you have 6,6Cooldown on fear
+Spammable and annoying Silence
+Good engage with Ult
+High base damage
+He is a CAW CAW

Cons

-Is very squishy
-If enemy team got good Map Control they gonna see your ult
-His passive can reveal his Position(Not fixed yet!)
-One of the lowest Autoattak base damage in the game.

Teamfight

You can choose here 2 Options,which depend on the setups:
Option 1:
-You stay around your ADC an protect him with your Fear/Silence (peel for him too!)
Option 2:
-Jump with your ult in front of the enemy team and fear the APC/ADC (NOTE: This would be very very Dangerous,because you are squishy and get killed really fast.

Option 2 is only good when u got some burster in your own team who jumps with you in front of the enemy ADC.

Option 2 Example:
Jungler: He would protect the ADC.
Mid: Would be jump with you in front of the ADC.
Top: Would be jump with you in front of the ADC.
Adc: PEW PEW PEW (:

Those ADC fits good with Fiddlesticks:

Good

+ 8/10
+ 7/10 (at lvl6+ the lane is stronger!)
+ 8/10
+ 10/10
+ 7/10

Bad

- She really needs a Poke Support like
- She needs a defensive support like

Those Synergys are my experiences from SoloQueue

Well this was my little guide.
I hope i could help you with Fiddlesticks support and i wish you good luck with him!
See you in the Field of Justice.