This Fiddlesticks build Concentrates on Ability power and although in the first 10 minutes of the match you will be vulnerable to death, by mid to late game you will dominate in not only team fights but also one on one skirmishes that occur in the field of justice.

I typically pick:

Clarity: Fiddle is infamous for using mana
Flash: For when you need to make a hasty delivery.
Ghost: Just in cause your too bad *** for heal

NEVER USE:
Revive: You dont plan on dying so no
Heal: You will be healing with drain so whats the point.

All the rest i dont recommend but can be used well with fiddle.

Be sure you last hit minions with darkwind and regenerate hp with drain if your being harassed it is essential that you get lots of gold for your items.

typically middle or top for fiddle so he can provide backup for those in need. Situational awareness is essential for your team to thrive so keep an eye out for potential ganks.

When jungling fiddle is a perfect candidate for ganking enemies who are fleeing especially when fiddle has the blue buff he can be a great asset to those champions who need assistance.

Be sure to farm mostly and harass when the champion gets a bit greedy usually go for the kill if the enemy has 3 bars or less but other than that just keep on last hitting those minions and get enough gold for you weapons.

By this time you should be getting some of your ability power weapons and gang fight will be becoming more common be sure to wait to use your ultimate until the time is right (usually when 2 or more champions over commit) Whilst your ultimate is going it is imperative that you DRAIN the first person who is closest to you as this does insane damage to the enemy.

this is where fiddle can shine gang fight are at a high and you have an insane ability power just be sure to do the ultimate/Drain combo for maximum damage and if they run out of drains range send darkwind and terrify is slow them down.

In gang fights fiddle dominates but he does still need his supports and tanks to take the hits to be an overall good team mate in a gang fight heres what you need to do:

1: Make sure to engage the enemy for your allies then quickly back out.
2: After engaging the tank should roll in be sure not to get too wounded but still offering support by harming other champions.
3: Once the tank has retreated pop your ultimate/Drain combo to make sure that any wounded champions on your side can flee and killing any wounded enemy champions and chasers.

this build does not make you invincible it just makes you a powerful enemy on the battle field and an even better ally. Make sure that when you engage you have an escape plan like Terrify ready and you will be an awesome fiddle in no time!!

AND MAKE SURE IF YOU INITIATE USE CROWSTORM IT IS ESSENTIAL TO YOUR TEAMS SURVIVAL IN GANG FIGHTS!!!!.