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.
Jungle starting with the big wolf only, then go for golem , finish off the other two wolves,kill the wraithes, the golems and lizard (you may want to back and it`s ok). Then kill the neutrals as they respawn. If you want you can gank once you are lvl 4 (you should have all your skills)
Gank-jungle-gank-jungle that´s all you need to do. And don´t forget using your ult with tanks that should be a great advantage for you and your team.
Trundle is a great support champion, so use your skills wisely, Rabid Bite for dps and Agony with tanks, Pillar of Filth for chasing or escaping and the same for Contaminate which you could also use for towers and any fight.