What's current meta for junglers? I know tanks are still good even with cinder hulk changes, but what's the popular routing, what Champs can gank first clear and which require teammates to hold on for a while, etc. How do I know when to go cinderhulk> stack hp vs armor? Are any carry junglers viable at all atm?
Right now my jungle pool is like, olaf/nunu/trundle/xin/naut that I'm super comfy on, then sion/gragas/vi I'm okay at but don't quite get how to build/what plays to make, and I'm going to learn sej/Lee at least soon. Which ones should I focus on? I know sej/gragas/hec are really good junglers right now
The meta is still tanks (fairly) but carry junglers like Lee Sin and Nidalee (ew) are returning to viability as well. The theme of the jungle meta for season 5 has been and continues to be junglers who can gank early and gank often (which is why Sej/Gragas/Reksai are so popular).
Whether a champion can gank (effectively) before level 6 is largely reliant on both their kit and what your laner has. For example, Gragas can gank for days because he's got that knockback and the slow, while someone like Nunu doesn't have much to bring by way of ganking power due to his lack of CC and damage, and champs like Vi/Warwick lack decent CC until they reach level 6. If your team has something like Twisted Fate though, he's got the Gold Card targeted stun to lock down the enemy laner, then a damage-heavy jungler like Olaf becomes all the more threatening in a gank.
Things like item builds, jungle routes, and whatnot have too many variables - it depends on the champion you're playing, the role you serve on your team, the team composition you're up against, and who is ahead of who.
As for the junglers you feel you should play, just stick to what you know, that's going to be what wins the games. If you're looking to stick to the theme of early ganks and try to snowball your laner, I'd go with Xin, maybe Gragas. If you feel you need to learn other junglers, then by all means take the time you deem necessary to learn all their bells and whistles.