Hi Folks, just doing some experiments with Jungle Diana for patch 4.20 and I'm going to keep working on this guide between now and Xmas.

I've been playing Diana since S2 but didn't try her in the jungle until S3 - but I just love it especially in a mainly AD team comp.

I wouldn't really trust my overall skill of the game - I play casually and over in the OCE realm - I'm just going to share my thoughts on a niche gameplay style that I love.

Playing as Diana, you've got the strongest Level 1 shield as a jungler (Karma & Janna don't count sorry) as it shields about 100 damage after all the orbs have been popped and does a lot of damage in the process. This is a must at Level 1 for any jungle Diana.

You're not going to come out of the jungle with any amount of health for a gank after your double buffs - so don't bother skilling Moonfall until you've backed and cleaned out your wraiths while sweeping for river wards. As such - this brings me to your jungle path.

Start:
You shouldn't start on your blue buff - get a good leash on your double golems and proceed to red. Depending on how healthy you are after cleaning out your wraiths (this is where I'm going to be doing my testing) I'm hopeful you can go wolves AND gromp (getting Level 4 on Gromp I think) and proceed to back (make sure to ward your blue in the process).

Ganking/Invading pre-6:
Because of the slightly different backing time compared to other junglers, you'll either be at a slight advantage (farm junglers go back after wraiths and not having extra wards/pots) or disadvantage (gank/invade junglers will complete their double buffs and gank or invade while you are back leaving your laners vulnerable for the time) so this is your time to make your move. Get your blue buff and smite their wraith camp to clear the river and gank for your midlaner (you will be level 4 just in time for this so get your Moonfall). Between your AoE damage and your quite seriously broken level 1 slow (only thing worse is Nasus or Singed) you will be clearing the wave and chunking their midlaner - and depending on your success, stay and get the mid-lane tower to force their jungler to cover before backing or invading further.

Ganking post-6:
I don't like invading at this point because your ganks become terrifying and if you've done your job properly it's no longer invading but rather controlling your opponents jungle. The reason why you've kept your Q at Level 1 is for this moment - Q into the minion line with your arch but obviously try to hit the champion you are ganking and then follow in with your long range R either directly onto the champ if you managed to hit them (if you didn't - just get into the minion line). Try to save your Moonfall until after your target has flashed - you have the choice of follow flashing or consuming your ultimate to chase if required. If they've gotten away and you've only burned your ultimate, that's a good thing, just go back into your own jungle and clear any camp (literally any camp) and your ultimate is back already.

Okay - there will be a lot of questions regarding the Core Build for this because most Diana's do not build these items, let me explain.

Diana's prowess comes in the form of assassination from the jungle. As with ANY jungler, speed is key, both in getting to your target and speed in reducing their health-bar. This is the reason why Lich Bane is a must on her as her first item (other than boots and jungle item), not only does it give her movement speed but it allows her to chunk down any target she flys on. I have tested this so many times, there is nothing better for mid game than it for Diana.

The other question is going to be in the form of the Rangers Trailblazer. Most people will be wondering why not Stalkers? If you can't kill your target within the time of your Moonfall wearing off, then you've probably used it too early, as mentioned in the Ganking Post-6 section above - save your Moonfall until after your target has flashed and either follow flash or burn your ultimate. As such I would prefer the health/mana restore and reduced Cooldown.

I have a habit of writing tl;dr versions of guides, so I'm just going to say that my normal round-out build for Diana ends up as the Core items with Nashors, Zhonyas and Deathcap ... but those 3 are all situational.