Which champion do you think i should add to my roster of jungler?

I have recently been playing a lot of jungle so i can have more than just supp and top as my roles. I'll list the jungle champions i own in order of who i am best with and i want the communities opinion on whom i should buy next. (this is for the S5 jungle because i don't know who would be best)

Going in order from best to worst

Udyr- This is my best jungler by far. ive already played him in the new jungle and i do fairly well with him. Warwick- First jungle i learned and i heard he was really good in new jungle for sustain. havent played him yet though Amumu- played him in a ranked match in new jungle (on accident). i did kinda bad but are mid carried. dont know if i should play him this season Rengar- Played him in old jungle and did really well. Shaco- played a few times didnt get the hang of him Master Yi- played 2x did really well Nunu- haven't played yet but his insane amount of sustain probably makes him tier 1 in new jungle. Right?

The following junglers i own but have not played. Xin Zhao Fiddlesticks Evelynn

Based on my Best to worst what jungle champion should i buy next?