After the new visual/gameplay upgrade for Trundle I decided to try him out as he was free, and I must say I was positively suprised. I liked his mechanics with his decent clear speed and potentially excellent gankes with his E. I have now played 50ish games with him and thought I would make a guide on him to perhaps invoke a more positive approach toward him.

+He has a decent clear
+Good ganks if you land your E
+Good sustain
-His E has quite a long cd early on
-W can point out your position to enemies
-No AOE damage
-No hard CC

For the basic build I suggest going with AD marks, flat armor seals and scaling MR glyphs along with lifesteal quints.
This will give you a bit of extra sustain and faster clear early

If you decide to go all out offensive Trundle I suggest Apen marks and quints alongside scaling MR glyphs and flat armor seals.
With these runes your first clear will be a bit slower, but you save money and an inventory slot in not having to buy Apen items

For the basic build masteries are standard jungle bruiser masteries, not much we can do there.

For the full AD build you could arguably go as far up into the offense tree to get sunder, but I personally prefer to take a more defensive approach mastery wise.

Leveling up your Q first is a must as it is your only means of counter jungling, because you don't really want to reveal your position by using your W. You could level your E before your W if you were to gank a lot,but normally you will benefit from leveling you W.

On the side of using your skills I suggest going into a custom or a bot match to practice hitting your E, but otherwise his kit is quite easy to get used to.

Firstly you should know the basic rules of jungling.

1.BUY WARDS!! (quite a lot of low to mid elo junglers don't realise their job is to ward)
2.Give away your buffs (the apc needs that blue buff more then you do)
3.GANK (winning lanes is more important then you getting your cs)
4.DON'T FLAME A LOSING LANE (babysit them, the flaming won't change a thing)
5.Counter jungle
6.Keep timers on buffs, dragon and baron (it may seem kind of dumb, but it is really quite useful)

When you counter jungle you don't want to use your W unless you run into an enemy and need to run away, as it tells the enemy that you are in their jungle. Use your E if you are unsure of if the enemy is in a bush or taking a buff as it grants you vision of the nearby area.

As for ganks you should try to lock an enemy into a corner or force them into running towards you with your E. Your E can also be a useful counter ganking tool as you can stop an enemy advance on to your laners