I do not want to spend a whole lot of time on this guide (fancy icons and stuff like that which takes an extra three seconds).
However, if you enjoy reading, then this is the guide for you.

Fiddlesticks was one of the early champions to be released in League of Legends and also has the longest Fear in the game standing at 1.25 / 1.5 / 1.75 / 2 / 2.25, which is his Q

His W is called Drain with a range of 750 and lasts for five seconds, which is partially the reason why Fiddle can solo Baron at level 4 with the proper buffs and items.

Fiddlestick's E is a silence (Silence) that bounces around up to 5 times that deals magic damage and silencing the enemy or enemy minions for a short duration.

His Ultimate is where you scare the enemy by standing in a bush. You jump (teleport) out, and yell CAWCAWCAW and possibly annihilate the enemies. This ability lasts for 5 seconds.

You can build a lot of different Runes for Fiddle, but the one that will probably help beginner Fiddle players the most is:

9 Greater Marks of Magic Pen. (+0.87 Magic Pen.)
9 Greater Seal of Armor (+1 Armor)
4 Greater Glyph of MR (+1.34 Magic Resist)
5 Greater Glyph of Cooldown Reduction (-0.83% Cooldowns)
3 Greater Quintessence of Ability Power (+4.95 Ability Power)

My reasoning behind the glyphs is because Fiddle can be bullied fairly easily in the jungle, so by adding cooldown, you fear will come up sooner in case you need to run away, or peel for an allied champion.

You can also do full cooldown, that works too, but if you are new at Fiddle or want to experiment in changes, then this is what I recommend.

I prefer Utilities Fiddle for the early Dragon and counter-jungling help.

So, with my masteries on the Fiddle jungle, I go 0/9/21.

For defense, I put:
2 Block
2 Enchanted Armor
2 Tough Skin
1 Unyielding
1 Bladed Armor
1 Resistance

For Utilities, I put:
3 Fleet of Foot
1 Scout
3 Summoner's Insight
1 Alchemist
3 Vampirism
1 Culinary Master
1 Wealth
3 Expanded Mind
2 Inspiration
2 Intelligence
1 Wanderer

Again, this is my personal preference. If you want to go 21/9/0, then be my guest.

I am not going to go into full getting items according to how the game goes, I am going to give you my standard Jungle build for Fiddle.

First, you start with a Machete's and five health potions with a trinket.

First time back, you start building your Ancient Golem (To prevent from being bullied + the CDR) and get a pink, plus two sight wards, and switch out your trinket for a Sweeping Lens and refresh your health potions.

(About this time, you'll be going to your bot side buff. Before you go to the buff, throw your pink in the dragon bush and if you don't know where the enemy jungler is, then throw the sight ward in the wolves / wraiths and also their bot side buff bush. (If you can smite steal the buff, go for it. It'll be useful for dragon if you can get the buff, or even better, kill them and steal the buff.)

Around this time, you should have both red and blue buff after you do your clear if you didn't invade the enemy buff, and is fully capable of soloing dragon at this point.

Sweep the dragon pit, leave for about three seconds, and go in the back of the dragon pit (You don't realize how many people don't pay attention to the mini-map and they walk past you while doing dragon, and they have no clue.)

The reasoning why you should walk to the back of the dragon pit is in case they find you at dragon and decide to kill you. Don't get nervous and Flash over the wall immediately, just give it a while and then if you think you're going to die, then go ahead and Flash. (This only applies if you are on blue side.)

If you are on purple, Silence the dragon and pull it out of the Dragon Pit to prevent a Smite over the wall steal.

If there is no trouble around the pit, then dragon will be easy. Throw your silence at it first, and then drain. While you're draining, just pop the biscuits from your handy Utilities Masteries and continue doing that process. It'll take about 40 seconds to a minute. The wards you placed in the enemy bot side jungle will help you not be nervous for the enemy jungler to spontaneously pop out of nowhere and kill you or the dragon.

MAKE SURE YOU SMITE IT.


Now, you just make sure you keep the timers up (buff 5, drag 6, baron 7). Simple enough.

ITEMS BUILD:
Spirit of Ancient Golem
Boots of Mobility
Zhonya's Hourglass
Void Staff
Abyssal Skeptor
Rabadon's Deathcap

(Again, this is a generic Fiddle build. There are multiple builds you can do with him, but this is if you are new to Fiddle.)

Your first ability will either be your Drain or your Silence.

DO NOT PICK AN ABILITY UNTIL THE BUFF IS ABOUT TO SPAWN

The reasoning behind this is in case of an invade, or if you plan on invading.

For an invade, get your Silence and then get a hard leash to smite.

If not, then get your drain, decent leash for quick clear, and smite.

After that, the skill sequence depends on either offense or defense.

Offense:
Drain First
Fear Second
Silence Third

Defense:
Fear + Drain. You will need to rotate will fear being the primary max first
Silence

With Fiddlesticks Jungle, remember he is still squishy with the Golem, however, this guide will maximize your playstyle to prevent you from being bullied and to help you get faster cleartimes due to cooldowns.

Again, this guide is for beginner Fiddlesticks players and is a generic guide with a little of my personal tweaks I prefer on Fiddle.

Stay awesome, Summoners.