This build focus's off having your cd low all the time, because drain is what keeps you alive, and being able to constantly drain will save you. Starting off with these runes/ masteries will give you approx. 30% spell pen off the bat, and by the time you really need the ap which is lvl 6, the ap per level runes will come close to surpassing the flat ap runes.

These masteries work best because at lvl 3 you will have rank 2 drain, and ignite is usable during your drain, which will equal a guarantee kill 1v1 whoever it is, unless you are matched against a person who can interrupt your drain somehow. The flash is pretty standard, i use it offensively tho, I use it to double flash to a point after I use my ult, which allows me to gank from a fair distance away.

The point of the elixir of brilliance is to constantly buy it after you get your ult so you can use it before your ult and have it off cd asap. If you are able to buy the needlessly large rod right away instead of blasting rod, purchase that first. If you are short of the large rod, the blasting rod + elixir will make up the ap difference.
Get abyssal staff/ rylai's sceptor and Hourglass in the order which you take the most damage in. Get the elixir of brilliance whenever it comes off so you can pop your ult quickly again

Dark wind is taken first because it provides the most damage initially and gives you a silence. However, dark wind is used mainly just for the silence and is really only needed after one gets their fear to at least rank 3. However, drain is maxed first, and fear should always be kept 2 levels ahead of dark wind so you can keep a target feared longer for the cc needed for your cs or drain.

This is a guide for how I play fiddle and from what i've seen it works the best. People always go for the dorians ring, but I don't like using the starting items because they don't build into anything, and if you have boots and 2 health pots you are good to go for a long time. Save your dark wind for last hits, or to harass the opposing champion, and the early boots are nice for some speed once you get your crow storm. Because of the runes and masteries I don't see the point of having the sorcerers boots, as you are good on spell pen for at least the 20 min mark. The cooldown boots will get your abilities back up and keep you alive and let you rack up the kills faster which I find is more efficient because it also allows you to build gold faster.

This build, runes and masteries supports an aggressive play style, I turret dive a lot, and when I play mid with fiddle, I get first blood by at least lvl 3, if not 2. I do this by slowly poking at opponenets health with dark wind and flash in to range to drain and ignite the other player.