Which Jungler should I get?

Jarvan or Zac. Since you are a team player.

skarskarskarner!

once you know how to land pillars he is really good ganker/splitpusher and is decent in skirmishing team fights not good in the full head on teamfights though he is not a tank like who is exactly what your asking for good ganks if you land hooks insane tanky. easy clears easy objectives and great teamfight champ although most prefer to play him toplane is great another tank champ that has ok clears and is not too weak and can ignore counter junglers like by just doing easy lvl2-3 cheese ganks.

Out of your list:

1. Zac - Zac is best on your list in terms of ganking and being useful at all stages in the game. He is almost always able to gank successfully due to the range on his jump. He is great for early skirmishes as long as his passive is still up because it counts as a pseudo-Guardian Angel--as long as the fight continues while he's dead, he'll respawn and be able to re-engage or run away. As his jump range gets longer, he can initiate/gank without fear of being seen by enemy vision and from unexpected places. Late game, he can launch into the enemy backline and disrupt carries long enough for his team to turn the tide or launch an offensive assault. His knock-up provides great CC and he can survive long into most engages due to his health stacking.

2. Skarner - Another great team-fighter, Skarner is great for running into a lane or teamfight post-level 6 and focusing down squishy carries. He can pull them into his team for quick and easy kills or ult an enemy jungler so Skarner is the only one who can smite critical objectives. A good flash-ultimate can turn the tide of games.

3. Jarvan IV - Jarvan is middle-of-the-road on your list. He provides lockdown on critical targets, but has to be careful if they have dashes or Flash. He has a critical knock-up that is crucial to ganks (so you'll have to grow accustomed to how it works) and he can boast heavy early damage, so ganking early is usually recommended. In team fights, J4 usually ends up being squishier than you like, so he's mostly about zone control and corralling certain enemy players.

4. Nocturne - Nocturne isn't necessarily a team-fighter, but he can initiate team fights. This usually draws most of the attention onto Nocturne and away from Nocturne's allies. Use this to your advantage if your team is fed. Otherwise, Nocturne is excellent at ganking with his ultimate, especially if an enemy lane is overextended. He can massacre carries that do not have defensive items as well.

5. Kha'Zix - Kha'Zix is the least useful in terms of team-fighting, but he is the most useful in terms of solo queue-ing your way to victory. Kha'Zix's ganks post-6 are very strong and, once team fighting begins, as long as he can deal a decent amount of damage, he can begin a reset train of squishy targets that leads to cleaning up a team fight. Kha'Zix is much more a snowball-assassin champion, however, and not too big on team-fighting. More like cleaning up after a fight or after it's already begun.