It gives enough wards for a while, good sustain in lane. If you aren't spamming E you should be fine on mana. Not only that but fiddle is squishy, and you're only going to have 1 point in W, so the opportunities to drain creeps/monsters is pretty low unless no enemies are around (which you can't always count on, especially if you fall behind).
Level 1 put a point in E for easy/cheap poke Max Q (taking W at level 4)
You're pretty weak compared to most supports until level 6. You don't have the poke potential like a Sona or Lulu or the kill potential like Leona or Blitz nor can you sustain your lane partner.
However, once you hit 6 you can pretty much all-in anyone. Hide in brush, wait for them to push to at least half way, ult in (make sure you have a decent idea where the enemy jungler is), Q the carry. Exhaust once Q is up then flash to follow if they try to run away.
A kill is pretty much guaranteed unless the enemy support does a good job protecting the carry.
Mid game just buy a s*** ton of wards and either ward your jungle (if losing) or theirs (if winning). If you see an enemy nearby and alone in the jungle, ping like a madman for your team to kill them. With a 3 second fear you're literally going to kill anyone.
Teamfights just use Q to peel for your carry then ult in and do massive damage. If you can buy one big item after boots/sightstone, I would definitely opt for Zhonyas as not only does it allow you to use your ult to the full potential, but it also is a huge distraction, especially at lower elos. Basically: Fiddle ults in. Since the animation is so obvious, people are going to be worried about killing you. Pop Zhonyas and now they can't. Now they know you are squishy and will want to kill you once your vulnerable again so they will wait and not really do anything for 2 seconds while your ult and the rest of your team kills them.
You place your mouse over a different champion, and pick another support that won't completely fall off.
Just played a game a Fid support and my Fear was one of the only reasons Quinn didn't get 1v5 pentas before Vayne got to 6 items.
So yeah, what everyone else said about maxing Fear first and using your ult and/or Flash to initiate teamfights. Fear whoever's most powerful at the time and silence whoever you want with your crow.
As for items, go with standard support items like Philo Stone and Kage's and you can get things like Locket. Then you can get standard Fiddle items like Spectral Wraith if you want to kill baron and dragon faster and Zhonya's will help you survive longer in teamfights.
For boots, definitely get Boots of Mobility. You can easily cut off fleeing opponents and fear them so the rest of your team can catch up. Merc Treads would be nice if the enemy team has a high amount of cc, but any cc will cancel your Drain and you should be able to fear them before they cc you.
Generation 30: The first time you see this, copy it into your own signature (on any forum) and add one to the generation number. Social experiment.