I updated this guide so i really want you (readers) to vote and make constructive comments about it. First of all, English isn't my mother language so in some areas i don't get much comprensive as i want, so i hope you undestand even for the grammar faults.
This is a Fiddlesticks -my favorite champ- guide, for jungling. Very easy you will dominate the jungle instead.

About the Runes.
When you build a Fidd you have the hard choice of putting much AP on Runes or going for the support for the AP (Magic Penetration, Cooldown Reduction, etc.)
But i think that is better to start with a lot of AP in the Runes and put the masteries on Utility cause there are no runes for those buffs.

I don't think that you have to put Runes or masteries on armor or HP, etc... with Drain you can be a lot of time out there and no recall... You don't have to recall... the only thing that can make the ganks more difficult is the mana thing if you don't have the Blue Golem buff ... for that reason i put a point on the Masterie Shrine. You have the time to finish your jungle and still have some aura to gank or go for the other jungle. With shrine you can finish your jungle and still have the buff.
Also... you don't have to put runes on the Mana thing... you will always have to go for the Blue G thomana regen.

I don't put points on the masteries for gold or exp because i preffer to be fast enought to don't need those masteries... those masteries depends of the time, same as the Item Rod Of Ages, you will never know how much time you will spend on a game (for that reason i avoid that runes that says "per level") i going for a secure buff at the start.

With you cooldown reduction you can cast Drain instantly after a Drain is finished, same as Fear... Fear is the best CC when you are 1v1 or when you have to destroy a specific target.

This build is based on versatility and good damage.

As you can see i go for AP... I think that put money on HP is useless, i know that Fidd is squishy and have problems with HP and armor, BUT putting effort on trying to avoid that problem is losing money on his really utility on the game: do sick magic damage.

I like Will Of Ancients cause when you cast Crowstorm in a area of 4 enemies is very probably that you will be the easy target, for that reason Spell Vamp can make you live until you mates come to your area of damage and get the kills or the assists. Remember that you can pass trough the forest and walls with Crowstorm. Also, you can tank with this item on a short time and finish that rush with no wounds. Is also good for tower diving...

Is very important if you are jungling to buy the boots, go for Magic Penetration ones.

Sometimes i farm Tear of Goddes to buy Archangel after the Rabadon, with Archangel Staff you will never have to recall for mana or going for Blue if you have that problem... the idea is cast! cast! cast! cast!
With Archangel you don't have to say "sorry guys i was in Blue trying to have mana for the teamfight that we lost seconds ago".

But now with Athene's Unholy Grail everything gets easier cause it gives you CD, AP and Mana Regen... i really love it! Is better cause it gives sustain if you don't have the blue and it makes the jungling more easy. With Fidd is very useful to have low CD... specially for the Fear... if you have a CD of 6.6 (Blue + Athene) your oponent will have 3 seconds to make something... on those 3 seconds you can silence him or drain him until your next fear is up.

Why do you need HP if you can do a instant kill? On 1v1 with a AD, if they don't think on the CC you will have the avantage cause the Drain... he will be hitting you while you are recovering your HP, the only think that you have to worry is for have a Drain that can resist those hits, for that reason go for AP and Magic Penetration with Abbysal.

Rylai is to give more CC to your spells... imagine your oponents trying to leave the AoE of Crowstom while they are slowed + 1 that is feared lol + some silenced guys.

For jungling: DRAIN, good work
LOL

The idea of put points on Fear or Dark Wing it depends on the situation or how is the game going... if you want to gank do you have to Fear, if you need to farm or push go for Dark Wind.

The first thing that you have to do is ask for the guy who is near the BG to take care of you... With Smite all the enemy team will know that you will be Jungling, so you need to take care as you get the BG.
Having it you go for the Wolves, then the Wraiths, Red, and the Golems... You can go for the golems first if you want to recover your self (you have Drain lol), and then the Wraiths again.
Try to gank mid before you have Crowstorm, and then go for the other Jungle...
This takes few minutes so you will be ready to be useful in every part of the map.

And important thing is to master Crowstorm, your position is everything. When you are jungler your team usually ask for ganks, mostly the Solo guy. Well, the bushes are a good way to take a good teleport into the fight.
Helping the solo guy is very important, you always can take Lane if you feel that he will lose the tower. But is a good way to attract enemies to a free kill... The solo guy is usually hug to the tower if the 2 enemies killed all the minions, so they will be near of your tower too... you can pass trough the wall or hide in the bush of the river. This probably is your 2nd or 3rd gank... the 1st usually is on mid.
You have to pay attention on all your enemies to gank and to do a good route trough the jungle to reach them.

About the Counter Jungle thing... If the enemy team is smart and your teammates don't trust you (lol) there will be like 2 or 3 guys waiting for you on your Blue. So ask for blocking the jungle and call for the mias... with Fidd you are a easy target. Other point to have in mind is the wards, guys, don't spend money on that -only if you are really scared-... better to be strong when the enemy jungler or counter junglers appear, you have to be aware of THEIR wards, that can represent a problem for your route.

Againts other junglers, the best thing to do is be more fast than they... if you meet him, the technique is to hide in a bush and then the typical Fear/Drain/Dark Wind/Drain/Fear/Drain.