Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
It is my Trundle dmg guide
At first buy dorans blade for more life and dmg (2).
Play defenes try to get lasthits on creeps. Only Atack heroes if they do mistakes.
Then buy boots you need berserkers for atackspeed.
I like Brutalizer next but dont finish it yet. (a full trinity force is better if you are feeded).
Now you can try to atack if you have a chace to build your e ability behind one enemie you and your mate can atack use ur surmoner spells and use the surprise that you do mutch dmg. Dont forget your ulti to be sure that you win. The ulti have not mutch cd.
Then buy a Infinity Edge or an Bloodthirster for dmg (nice for you q ablility).
At that phase of the game try to gank mutch and get gold in the jungle.
At next buy the sword you dont have. (Or when you die to often buy sunfire for psych dmg or benshees for magic enemies).
In the last periode of the game go in fight as the 2 or 3 one and do your ulti fast on the enemie tank. Then fokus one low hp hero or the tank(he have -20-40% armor).
At least buy phantom Dancer buy a secound Bloodthirster and finish your Ghostblade.
Now you are a glass canon who can get mutch amor with the ulti. You do Massive damge and noone can escape because you are very fast and your stone block the enemies.
The Importent things :
I take only crit runes because you dont need amor pen ... you ulti do it.
Use ur ulti to gang enemies you are very strong in 1on1.
In 5vs5 fight do you ulti on the tanks to get amor.
Try to get the buffs(blue and red) to spam the q ability.
Test it and have fun.
If you have questions ask... and if you know what can be better say it ;)
Sry for my bad english but its not my faforite language ^^