Hello everyone!
This is my first guide and i hope that you can all judge it accordingly :p. This guide is about Trundle who is my favorite champion and i have many games completed with this underplayed champion. I have gotten very efficient with his jungle route and perfecting his build. Please enjoy!

I feel Like these masteries complement Trundle very well while in the jungle. With this build you get maximum extra damage to the monsters and get very fast laps.

While using Trundle as a jungler you should focus on speed, which is why i grab Ravenous Hydra before Frozen Mallet, however, if you cant get your ganks in without dying or losing too much health to continue jungling, get a Frozen Mallet first. With these items you should be getting enough life steal to get your health back to full after a lap and a half of jungling, if not faster.

Very Basic sequence for Trundle. Max out Rabid Bite first, then Contaminate, Agony, and finally Tower of Filth.

Smite - A MUST have for jungling
Flash - i prefer Flash to Ghost because Trundle has Contaminate and tower of filth to get away and close gaps.

Overall Trundle is in my opinion the best underplayed champion there is. If you can get a good jungle route off with a gank or two you will be set for mid game and be able to carry the team to victory during late game.

IMPORTANT - use the starting 5x health potions in between every camp starting after wolves. if this is not done then this route will not work and you will be killed by the monsters as you do not have the life steal to survive in the jungle yet.

To Start, Spend you point in Rabid Bite and buy a Hunters Machette and 5x health potions. Get the middle lane to help at blue, use smite. Spend your point in Contaminate. Go to Wolves and use Contaminate at every camp from here on. Move across mid lane to the Wraiths. Move up / down to Golems and focus the larger Golem. Use smite on the large golem and use your point in Rabid Bite. Move back down to Wraiths and then to Wolves. Alternating on these two camps until smite is up to go back to golems. Once your finished with the 5 potions go back and buy Madred's Razor, go to wraiths and then to Red and start a gank on top or bottom if top is doing ok. Continue doing this route and you should get coins very fast for your item build.

Pros-
Very good at closing gaps / getting away
Agony makes the opposing tank useless, allowing your team to focus the tank at any time
Fast jungler
Great Ganker
Cons-
Other players dont like Trundles on their team :(
One damaging ability
Can be difficult to learn

As you are ganking start with a Contaminate in the area of the victim. Put up a Pillar of Filth directly infront of the enemy blocking their path to their turret, also stopping a flash. During big team fights put a Pillar of Filth up in the beginning in the middle of the enemy team. Contaminate that spot and go in with your team. Using the Pillar of Filth in the beginning makes it so that you can use it again to prevent someone from getting away at the end of the fight.