I've done the jungle with Xin and Udyr, but with Udyr i'm terrible player, i don't know what to do. I've noticed that:

• I can't gank as easy as Xin, The E isn't enough because Udyr is melee, only with flash but this has a long cooldown.
• My time on jungle is decent but Udyr waste a lot of mana if you use R->W->R->W. With the Blue Buff it's fine but without this... even with PS.
• Against junglers as Maokai Udyr can steal his jungle but against Junglers as Xin, Nocturne or Lee Sin he can't do it.
• I'll build tank items but i don't know what to do, i don't know if he should initiate the battle. I think he can't initiate a battle.

Udyr you have to choose either tiger or Phoenix, you can't level both and expect good clears. Start with one point in Phoenix, then turtle, then bear, then turtle Phoenix until phenoix has 3 and then go turtle bear tiger. When clearing camps go Phoenix and right before the 3 second buff clears hit turtle so you max that passive but are still using the max amount of each stances active.

UDYR has to know which lanes are warded or he can't gank, flash in mandatory because he has no gap closers or openers. Build him tanks with a little bit of damage. Frozen mallet is a must l, would've posted something much more informative but I'm on a phone. Hope this helps.