Hello.
I am simply your standard hard-stuck.
I made this build randomly in a game when my team had two junglers and I expected an instant lost at 15 mins, so I just started building crit. For once in my LoL career, we didn't lose; and I found that going crit made Trundle go brrr with crit.
This is my first time actually writing anything inside a random build I've made, so it will definetly not be pretty... So please bare with me

Update:
This is my current winrate with this build in preseason. (Please note that these stats are from the same game that I started the build with to now; I'm currently playing low-elo, so I can't say you will see the same results in high-elo, if someone does get it, please send a comment! :D).

PROS + Insane damage + Good mobility + Good in teamfights + Split-pushing god + Is dangerous from level 1 to 18 + Can carry games

CONS - Too much CC is a counter - Will be targeted - Dashing champs will escape

Okay, so the thing is that since your Q ability actually does crit, you utilize more than just your autos. This makes it so that you basically become Trynda 2.0, more dmg, cc and speed, with the only thing laking being the immortality (at least in a spell-form).

- Early Game -

I always start DB and Potion, since I feel like this is working the best for me. If you'd like, you can start DSinstead, if you feel like being more defensive in your laning phase.

My first back-buy will depend on matchup and more importantly - gold. I will prefer to get Tier 2 boots, usually Berserker Greaves, Refillable Potion and a Pink ward. If this is not available too me, I'll buy Long Swords, Daggers, or Tier 1 boots.

- Mid / Late Game -

After you are done with your Core, I choose my items depending on a two main things:

-Enemy team comp
-How far ahead I am

These are some explanations to what items to build, depending on matchup:

(Please note that you yourself will have to choose what item to remove to fit these in, it will be depending on your game!)

I will build this if they have a lot of CC, or possibly if they have a lot of magic damage.

I usually build this when going against a bruiser (or bruisers), quite good damage, and the mana regen is very nice.

I build this if the team I'm going against heals a lot, it will help you immensely.

Okay, this one is quite simple. Is their team tanky? tImE fOr pEnEtRaTiOn ;)

So, this one I buy if I feel like I need the movement / attack speed. It is quite good, but I don't build it that often, since Trundle goes *brrrrrrr* anyways.

So these are the usual items that I choose between during my game. If you find some other godly item, use it! :)

SUMMONER SPELLS - FLASH: Flash is a must. The mobility you recieve is needed, especially when meeting dashing champs. It can both help you escape, and also chase champions that can wall-jump. The only time I'd choose something like Ghost over Flash is if the whole enemy team is "non-dashable". IGNITE: I usually don't play with Ignite, but it's a great cheese-tool in the early levels. It gives immense damage, and the healing reduction early is insane. This will be my number one spell when they have nerfed the Teleport. TELEPORT: I usually play with Teleport, and the reasoning is: 1: You can get back to lane fast if needed. 2: You can help your team with teamfights or objectives a lot faster. 3: You have the ability to split-push a lot easier.

PRECISION

Lethal Tempo is in my opinion the most broken rune on Trundle. He is already good at taking short trades with his "AA -> Q -> AA", but this makes it so that he can take even better extended trades or all ins. The attack speed is so good, together with the AA's range.

The reason I choose Triumph over Presence of Mind is that it gives you a 2v1 potential early. If you get ganked by the enemy jungler, and you get one kill, you heal quite a bit, thanks too you passive + Triumph. This might just get the second kill aswell.

The reason behind choosing Alacrity is quite simple: you want as much attack speed as possible. You could change this out tp Bloodline, if you feel like that is better, or that it would fit the game better.

I choose Coup De Grace because it gives the most damage out of the three (according to me, I'm hardstuck, so this is not 100%).

Why do I max Q first?
I choose to max Q first due to the damage and debuff it does. It gives you more attack damage, and taking it away from the enemy, and also slowing them. Besides this, it basically works as second AA, which let's you cancel your AA animation.

Why do I max W second?
The reason behind it is that it's gives too much good stuff. You get movement speed, which gives you the ability to ingange / disengage. It gives you attack speed, which is great when doing extended trades or all-ins. It simply let's Trundle be Trundle.

Why do I max E last?
It's simply because you only need one point of it during early / mid game. Whilst the pillar is great to cut of escapes, or letting you get away in narrow corners, it doesn't compare to your Q or W.

- Early Game -

Level 1 & 2

Be aggressive - Use your early game strength at lvl 1 and 2 to try and cheese your opponent, obviously, you will not be able to do this every time, but if you know your matchup, doig this will be quite easy, since many doesn't expect the insane attack speed Trundle gets at both level 1 and 2.

Level 3-6

Your opponent will probably have had their first power strike, and you should try to stick with short trades and farming until level 6. If you got a good early start with a cheese-kill, you might be able to take an extended trade, or even a kill. But be aware that it may hurt, or even kill you, depending on who you are against.

Level 6-11

You are still in laning phase, after you hit 6, you should be able to grab kills in your lane, if you use timing correctly. You should also look to grab Rift Herald, either by yourself, but preferably with your jungler.

Try and look for TP's bot, or roams to mid. After all, helping your team is the key to winning the game! Just make sure that you don't let your laner push the lane too mucb, try and ask for help by the jungler or mid laner if you are too far away :p

Level 11-18

You will at this point soon be in the late game (or have reached it alread), and your focus will be objectives and teamfights. You will be great at grabbing the back line, since you are fast as frick boooiiii and you also have your pillar to stop them. You will melt drake and baron, especially if you are with your team. Splitpushing will go fast as heck, so try and grab a turret at every oppertunity.

Even tho you are great at chasing as Trundle, don't do it too much, as you will probably end up getting caught by their entire team. But of course you should try to, if you want too, since those juicy juicy kills are just *toooo* juicy to miss out on. But if you do chase and get killed, but take an enemy with you, don't forget the magic word "worth".

At this point, you should have won, but remember, if you didn't... It was team diff ;)

There really aren't any "flashy combos" to Trundle. He is simple, but deadly. These are the two main combos that you will want to use when playing.
- Simple short trade combo: AA -> Q -> AA
- Extended trade / all in: E -> W -> R -> AA -> Q -> AA, if you still are going, just smash your head to the keyboard, everything should always be on cooldown.

Okay, so is this actually good?
Idk maybe, ask someone that can play the game, I'm just your average hardstuck league player. But in the experience I've had with it, it works.

Am I planning on adding more threats?
Idk, if I remember too. Currently I'm a sleepy boy and don't remember what is hard to go against as Trundle. But also, is there actually anything that is hard with Trundle? ;)

Will I update this?
Maybe, but I'm probably too lazy for it. :)
But, I have updated it quite a bit already, and I've tried to make it look better. I'm about to reach 24 hours without sleep, my mother took one of my monitors; so I'll probably work at it a bit here and there during this day, maybe tomorrow, but don't execpt this to work forever xD

GL, and don't forget: don't blame me for your loss, blame your team! ;)