Alright. this is where i see if people actually read the guide. THIS IS A CONCEPT BUILD. i have used it a few times and had good results. i understand that this is not how trundle is normally built. please dont sit there and tell me its all wrong just because its different. sorry for the rant. Now welcome to my Trundle regen build!

PROS:

Great ganking potential
great jungling capabilities
can maintain presence for a long time with his passive
excellent 1v1
Great versatility

CONS:

poor farming
heavily reliant on your W
generally used in fixed roles

Armor marks to help you in the jungle early game. this lets you survive longer and for more use. The rest all add to the regenative abilities of trundle. you want the regen because it adds so much.

you want the point in smite. i know that some people dont like to put the point in. i do simply because it gives you the extra gold and the 5 seconds off the cooldown. you want enough points in utility to get the extended buff duration. the rest go into defence to give you more survivability.

you may notice that every item but one is one the regen list. this is intentional. the regen gives you immense stay ability, while at the same time giving you all the other aspects needed to be both tanky and a good damage dealer. tiamat is actually in my opinion a very underused item. it gives you some farming potential and extra damage for your ganks. it also helps in team fights when the enemy is amongst you. in truth the order of the items being bought is, as always should be, situational to each game. the items above will work for most games. just buy what you need when you need it.

i put both these sections together for the simple reason that they play hand in hand with each other. you want to take rabid bite because it lets you get blue at first, then move through your jungle with ease. then go into contaminate to gain mobility and attack speed. the crowd control debuff helps a lot as well in team fights. you wait until level 4 to put a point into pillar of filth because this is about the time you finish your side of the jungle and this is a prime time to look into ganking for your team.
this is the jungle route i reccomend.
BLUE BUFF->WOLVES->WRAITHS->DEUL GOLEMS->RED BUFF

if you dont like going for blue first, then this may be for you
DOUBLE GOMES->WOLVES->WRAITHS->BLUE BUFF->RED BUFF

with the second route, i give fair warning. you will most likely be mana hungry and have to blue pill at least once.

your biggest thing to remember when it comes to team play is that you are not the tank. you are tanky, but there is a distinct difference. tanks initiate the combat. while you can initiate, i would not recommend it. the best way ive found to play trundle is that your role in team play is simple. gank during laning phase. then during team fights, hunt opponents who are out of position. there will most likely be at least one of the enemy team out of spot. by keeping one or more of the enemy team occupied, you let the rest of your team take the big fight, then help you clean up the smaller one. your pillar of filth helps greatly with catching the other players off guard and making them pay for bad placement.

so thats it! sorry if it seems boring, but im a low tech kind of guy. hope you enjoy this build!