Since i can't code for ****, ima just say whatever i want so bear with me. Fiddlesticks is a fairly verastile champ, he does some things well, and others not so much. As a jungler you need to make sure that you track the enemy and ensure that you do not get invaded. Level 6 is your best friend, your yasuo mid is not. Your blue will give you more than you ever want, your orianna wont. Level 6 is all you need before going on a rampage. Make sure to stock up on pinks and put them in high ward/traffic areas, you can also use them as support bait by putting them in the open and sitting next to it in a bush, lul.

Combatwise, you want to stay hidden and make sure you can get a good ult, a good ult will change the tide of a fight. Fiddle can pop over all the walls in the game and with the advent of flash/rb/e you can extend your fear range for pretty long. Basic combos would be casting r and spamming e in the desired location during the channel, The classic r w flash, by spamming w and flash during the r channel to extend the range and instant cast w on a feared target, and the notorious bush, w flash, where you cast w than flash a split second after.

Vision is perhaps the most important aspect of fiddlesticks, vision can save you from poor placement as well as a bad ultimate. Make sure the place effegys/pink wards before you ult and in spots that you might. As a fiddlesticks in a teamfight, your only goal is to 1 hit the backline, the sooner you do that the faster you will win.

My biggest piece of advice is to be paitent, dont get greedy, stay safe, give up a camp or two, and you can have all the revenge you want at 6.