Just a short guide of my own Diana build.
This is my personal favourite build for jungling as Diana. Here you will find out why I choose to build her like this.

9x - Greater Glyph of Shielding: For late game tankiness since i build her abit bruiser like
9x - Greater Mark of Alacrity: To proc her passive more often, those will help u clear the camps faster
9x - Greater Seal of Resilience: Better sustain in the jungle
3x - Greater Quintessence of Potency: She scales with AP so I picked these for more dmg

I've taken 9/21/0 I like to skill her masteries like this just to become more tanky, you can still do alot of dmg + jungling will be so easy with those tanky skill points.
I haven't tried any other mastery build but I think these masteries really work.

My reason for choosing these items are that I become more of a bruiser mid/late game and I like building my junglers as bruisers for the tankiness and still being able to do dmg. I personally like being in the middle of the fight and being abit tanky so I don't die in 3secs if I build pure AP.

X - Nice dmg + fun abilities
X - Pretty tanky with this build
X - Great chaser

X - Squishy early
X - Can't escape CC's
X - Pretty expensive build