A Fiddle supporter may confuse you at first if you're not used to him. But I can assure you that he can be a lot more helpful that you think!

*SPELLS:
I prefer Exhaust and Flash, the two standard supporter's spells. They may be replaced with Teleport if you intend to maximize the element of surprise / Fiddle's grasp of the map. I suppose Ghost could be effective with R but I wouldn't recommend it.

Fiddle's greatest strength as a supporter lies in his Q and E.

His E can be a nightmare to the enemy bot pair when there's no minion around; it will bounce off the two over and over and can reduce their health to half at the first try. Even with the minions absorbing some damage, you can help the ADC farm more effectively and silence the enemies at the same time. Fiddle's E cancels Thresh's pull when it hits him when he prepares his move (i.e. swinging the hook in the air) and prevent Leona from hitting the ADC. If your jungler and ADC are ready, you can let yourself be hooked/pulled/stunned and use E and Q at the same time and inflict significant damage on the enemies.

Need I say more about Q? It can save and end lives. Save your ADC and yourself from ganks, CCs and other moments of peril. The subject of the ability should be chosen carefully. In case of ganks, Terrify the jungler to prevent him/her from delving further into the situation. If the ADC has been pulled or stunned, use it on the enemy ADC. Q followed by E should be enough to save your ally in most cases.

W sustains your ability to stay by your ADC's side and maintain the line, but also to aid the ADC in attacking the enemy when he/she's been Terrified/Exhausted. I usually master this last because unlike the jungling counterpart, a supp Fid doesn't need a lot of sustenance himself.

The ult can be a bit difficult to use when supporting because your location is revealed to the enemies most of the time. The most effective way would be to learn which brush remains un-warded, and ult from there. In other cases, use it when your jungler has come to gank or during team fights. Ulting can distract the enemy's attack from your core dealers and onto you so you may end up dead, but damage and distraction you provide can earn your team an ace. Finish Zhonya as soon as possible to ensure your survivability.

*ADCS:
Fiddle can support most ADCs quite nicely. With champions with the ability to deal high damage in a short period of time (e.g. Vayne, Draven, Corki) Fiddle's Q can be incredibly effective, while Fiddle's E can supplement champions with long range attacks (e.g. Caitlyn, Ezreal). Fiddle can either help his ADC farming by just poking the enemies continuously and keeping them at the bay, or actively participate in the actual kill. Just make sure that you coordinate your attack with allies.

*Others:
Needless to say any champion with CC would be great with Fiddle. For instance, Zyra's Ult + Fiddle's Ult can be a pure hell for the enemy team.

*PROs
- high poking power
- most of his abilities can both deal damage and save your allies from danger
- self-sufficient; can stay by the ADC for a long time
- Terrify has an insane stun time (2.25s when maxed)
- Silence can deter especially threatening supporters (e.g. Blitz, Thresh, Leona) from finishing their moves
- E can safely finish off fleeing enemies with low health even under the turret
- RANKED: Choosing Fiddle when you're the first/second pick can throw the other team's decision making process by allowing them to believe that you're the jungler.

*CONs
- the Ult has less impact and is a bit trickier to use
- no healing ability
- becomes useless in an under-performing team because his items are expensive
- more prone to take the ADC's kill by mistake
- E can distract the ADC's flow of farming if he/she's inexperienced