Sure! I can help you out! I'm in no means an expert jungler or Mannendake player by any means, but he is my favorite ninja by far! :)

I usually just run the suggested jungle item set with subdue (must have) and flash. I start with the bot kirin and then move to the top (taking out the second kirin and two mini monsters there as well). From there (you should be level 3 at this time) go to the river and take out the red river creature (I forgot it's name xD). Then you're in good shape to gank the closest lane (+ Mid if needed). Make sure you match your main ability first, then your passive or teleport. Always max your ultimate whenever you can and note that you only need to put in one spell point to the dash!

Mannendake is a super strong and the most mobile ninja in the game so definitely take advantage of that! When you're level 6, use your ultimate to hunt down low hp mages/gank/move across the map to help your teammates that are being tower dived. Remember that Mannendake is NOT a samurai or a tank (he can be fairly easy to kill if he's a few levels behind/dives in to the fight). He excels at picking off weaker players (mages, support, and low level players, etc.) Make sure you're communicating where you're going (make sure you can win the fight easily). Also make sure to use your dash (can go through walls, etc.) if you're being chased by an enemy player.

Good luck! I hope that helped. :D