For example, Udyr can jungle very fast with Fenix Stance. And he has movement speed boost and stun with bear stance. He may not be best on a specif aspect, but pretty balanced enough to jungle, gank, survive, tank and support if need. Or Xin Zhao, who can do lots damage at lvl 3 gank. They are pretty easy to use and learn.
Other thing is you can notice how good are your partners in the begining when you are going to start jungling:
1. Which position they take to prevent a counter-jungle from enemies. (Before 1:40)
2. How they provide you the "Leash" at wolves/wraths & Blue/Red buff. (At 1:40 & 1:55)
Also during the early game:
1. When an enemy jungler come to counter-jungle, your closest teammates should be there with you to kill the enemy jungler before he gets out of your territory. You should ping and notice them.
2, When you want to counter-jungle, make sure that your teammate can support you if possible. You should ping and notice them too.
3. The position of each wards the laners put, depending on who is enemy jungler.
All these are evidence of how good player your teammates are.