Okay you are laning or soloing and you see a freaking scarecrow coming out of no where and fears you silences you and starts draining your blood like if its vampire. This is what fiddlesticks is capable of with debuff style skills like fear and silence with ton of damage out put with Crow Storm and survives from 10% hp to maximum with awesome ability drain. My build focus on Spell Vamp to maximize Drain with good enough AP and magic penetration.

For masteries i go with standard mage 9/0/21. As for runes i take magic penetraion Marks, ability power per level Seals, cooldown Glyphs, and flat ability power Quintessence
Skills I master drain asap since my build relies on spell vamp, but make sure to get both fear and silence before level 4 to gank. Unlike ult that you have to master whenever possible, fear and silence depends on the player's taste. If you are relient on your allies master fear first while if you are more of a solo player go with silence first. I prefer silence but due to fiddlestick's squishyness you have great chance to get slain easily so I rather go with fear to gank with my allies.

First of all you should get amplifying tome and health potion and go to blue golem camp, there wait until you reach 1:55 on score board and your blue golem spawns. It would be great if your ally can leash your golem but if not first start draining blue golem, right after your drain is on cool down use your health potion until you get your cool down for drain again, smite deals 537( i dont remember it clearly) at level one so smite your golem when it's hp is down to that point. Then go to wolf, wraith, and golem camps if you think your strong enough for lizard and have your smite just kill the red lizard before you get to the two golem camp. When you've done the first jungle swiping ( What i'd like to call it) try to go for enemy blue golem if not, search for the line that you could possibly get gank kill. After your first gank if you are fast enough your blue golem could have respawned for you to get it again. After getting you second blue buff you should go for gank again just as a jungler should do "HARRASSING AND KILLING"

After this routine if you have enough gold go get your soccerer's boots and incase if you have more gold even after you perchased your shoes get hextech revolver for your spell vamp.
Keep on jugling and when you get to level 6 usually team fights occur so stop jungling if you see anyteam fights start helping. Get blue buff whenever you can, its not just for mana regeneration but cooldown maximizes fiddle stick's ultimate irritating power LOL :p
When you get your ult try to use it inside the bushes or walls so you can give your opponents elements of surprise; use silence first while using your ult, then fear them while draining. P.S : IT's important that you find great places to use your ult without your opponent noticing it.

I usually grab will of ancients first then followed by fiendish codex for cool down and mana regeneration. The next item you should get depends on what status you are on, if you believe you are too squishy and low of hp get hextech revolver while you can get needlessly large Rod if you want more ap, but besure to get both items before you go on with other items. After that get hextech gunblade or death cap; then you go finish morello's evil tome for great cool down reduction finally getting void staff for massive amount of magic penetration.

PROS
- Fiddlesticks can easily harras ppl with various debuffs
- Its easy to sustain maximum hp using drain
- Damage output is amazing

CONS
- Has drain but low hp results in squishyness
- Real low magic resist making it easy for opponent mages to assassinate fiddlesticks
- Based on low mana and mana regeneration you might run out of mana when you need it,
be sure to calculate the amount of mana you need for full combo when ganking or fighting.

TIPS: You can alternate your build situationally getting arcangel's staff when you cant handle being low of mana, getting Rylai's crystal scepter to prevent being killed often, and could use abyssal scepter when you need magic resist or magic resist reduction having many AP champions on your team. I recommend getting rid of Hextech gunblade if you were to make alternation to the build.

Also, besure to get bluebuff everytime when available instead of getting mana based items you could get bluebuff instead: i mean... you are jungler and harrasser, you need to use abilities frequently.

Recommend using ult -> silence -> fear -> drain combo for fights, and dont go to forward cause you are easy target for ganknig.

Finally enjoy playing fiddlesticks, you can get cocky but dont do that too much though :)
This is the end of my guide to fiddlesticks vampire style build, if you have any suggestion or additional tips you can give be free to post it on comments below thx :D