Not Updated For Current Season
Low Level Dueling is something not often done in League of Legends, but it's a lot of fun; I encourage you to give it a try. Don't downvote the build til you do! Would love comments, criticisms, and suggestions--but remember: it's a general template! Adjust it based on the specifics of the game.
Meant for Twisted Treeline gameplay. Low levels (9-15) don't really know how to counter Fiddle. His crowstorm is a guaranteed kill everytime it comes up, and by the time you get Zhonyas you can flash into 2 or 3 of them, pop Zhonyas when they attack you, and fear/drain as soon as you get out of your statis. You'll survive long enough to kill 2+ and still be in decent health from the drain. It's obscene. Just hide in a nearby bush or in the dragon pen when you're ready to engage.
This build is very much centered around that strategy; the use of his ultimate. CDR, speed, and magpen are more useful than AP for Fiddle, as he has terrible scaling. This makes him versatile; add more life/resists as needed.
I suggest taking the top lane and boxing your partner out of the minions lane ASAP. Level 1 and especially at 3. Here's how. Pop out of the bush to get a regular attack off (or drain, if they're close enough) and pop back in to get rid of minion aggro. Repeat once more, or until they're at about 70% hp. Then, simply stand between them and the minions, sacrificing your last-hitting abilities, in order to keep them too far to get ANY experience. Use fear/drain (or just drain if you're low on mana/out of range) if they come to get experience. Simply pay careful attention to MIAs! At this level, most teams are not coordinated enough to send someone up to gank you and regain lane control. Often you can get a huge level advantage from the start this way, or drain a first blood if they underestimate you.
Even against a tough solo laner, Fiddle can calmly farm gold and lane exp forever. A powerful drain gives you unlimited HP (not instantly!) and Clarity should keep you in the lane til well over 2k gold. Feel free to do this if you don't want to try the aggressive laning outlined above.
While you CAN get away with initating w/ your Ult, it's not a good idea unless you're assassinating a lone laner. In teamfights, use your fear to save a low hp ally or to focus a carry. If focusing, use your drain to add extra damage, but you can also use it to bait your enemies into thinking you're halfway dead (then turn around, drain, and you have even more HP by the time it's over).This is especially useful for the 3v3 gank in the beginning, and getting you or your team first blood. Use your Dark Wind (E) purely for silencing, at least until it's level 4-5. Even then, it's more useful for breezing through the jungle or pushing minions. Also use it to finish an escaping enemy if there's a closer champ you can target with it.
Have fun! Let me know what else you guys need to know!