This is my Second build but this build is aimed around early game ability power followed my high amount of Mana

Early game: Start of by getting my dorans ring and my Drain and usually i keep hitting and running with my basic attack and then lure them out and Exhaust+Drain them which is quite a strong combo most games i can get 5-0 within 10mins which is normally when i get my Sorcerers shoes and a Blasting wand towards my Rabadon's Deathcap at this stage i go and get both buffs by using my drain for my health on them and then ganking low health people by 15:00 i have got my Rabadon's Deathcap and can solo drag which my technique is Drain - > Darkwind - > Drain and repeat until dead.

Mid game: by now i start aiming for my Archangel's Staff which will give me a huge mana boost and ability power. Shortly followed i get my Meja's Soulstealer and go ganking for stacks on it and bonus ability power if going right you should be on about 10+kills by end of rod of ages BUT REMEMBER TO ALWAYS KILL DRAG WHEN IT SPAWNS

Late game: soon i should have my second Rabadon's Deathcap and when i get it i am near on invincible normally i call my whole team to mid for a push to win the game which with my ability power you are almost certain to do a nexus turret push maybe even whole thing.

Pros
1) Fiddle can Fear and Silence enemy's.
2) Fiddle's Drain does lots of damage and healing making him very powerful.
3) Good against Non-Tanks
Cons
1) Tanks can be a problem (Jax ; Dodges, Pantheon ; Blocks and other tanks because of high Magic resist + health)
2) Not the best tank.

I recommend using Flash (summoner level 12) and Exhaust (summoner level 1) the reason for this is when using Fiddles ultimate exhaust can slow them down to keep them in your ultimate's range and if they flash out you simple flash back to them and fear them.

Ignite + Flash is a possible combination if your good at using your fears and silence's as you can use your fear to keep them inside your ultimate and still have a bonus damage from Ignite and Flash is always there to either keep up with your target or escape from team fights/hard fights.

Heal: i wouldn't recommend this as Fiddles Drain can heal just as much as heal and its not worth wasting a summoner spell when he can already heal fast enough.

Clarity: Clarity is possible but the amount of mana Fiddle gets is almost impossible to run out so i don't really see any need for clarity.