I'm just a tad bit new to level 30 and I know my rune choice is pretty bad but it's really all I got since I was building AD for my Tryndamere.
I'm gonna make this clear right from the get-go. I do NOT suggest doing this in ranked, at all. Although it's nice and such for PvP I have NEVER tested in Ranked and I don't plan on it.

Now this actually works and I have had so many people be really surprised when they saw I was grabbing smite with Mordekaiser

Make sure you gank a LOT. This guide is probably not the jungling guide for Mordekaiser that you can use if the enemy team has a jungler or else it will be a massive hindrance to your jungling and your leveling will go so much slower and believe me. That is NOT fun.

Pros

Levels fast in the jungle.
Kills wraith camp extremely fast
Can sometimes level faster than mid O.o

Cons

Very squishy until you have Warmog's
Has no CC to gank with
Enemy junglers can really cramp your jungle route some

I LOVE to spam Physical Damage runes for Mordekaiser when jungling because it makes his Mace of Spades better and that's pretty much his best tool for jungling. Of course you can always grab health runes or AP runes but my personal preference is the Physical Damage runes because it's 22 extra damage and some nice help with your Mace of Spades

I find 22/0/8 to be good for playing Jungle Mordekaiser because it allows him deal more damage than creeps and to get that nice extra gold from the Plentiful Bounty . Another good thing in the offense masteries for jungling is Offensive Mastery for the helpful AD against a few of the tougher creeps like the golems and such. I don't like building into Utility's Insight because for Mordekaiser you personally don't really need the buffs after level 6 and even so you should only really get them for ganks. However in Utility I love having Awareness because it allows me to level faster, which is really perfect for a jungler.

For jungle Mordekaiser I always try building a bit more Hybrid than Tanky AP because personally I find the damage to be better yet you still have nice health to keep you alive. Of course I like to take Madred's Razor early on to help me kill those jungle creeps pretty fast. I like to get boots before any other damage item because I need it to gank because Mordekaiser moves super slow and such. Getting Blasting Wand and Giant's Belt to make sure I have actual damage and life after ganking a few times. Getting Boots of Mobility afterwards for quickly moving around and to scare people when you run out the river with really fast movement speed plus ghost. Afterwards I get an Amplifying Tome so that I can build into Rylai's to stop people from escaping. Then I start trying to build into Guinsoo's Rageblade by getting a Pickaxe to further increase damage then Blasting Wand. After having my Rageblade I save up money for a Needlessly Large Rod which later turns into a Rabadon's Deathcap for that amazing amount of AP, after getting another Blasting Wand of course. Getting a Giant's belt and Frozen Mallet last for that HP bonus and more slowing.

I try to get Mace of Spades up to level 5 ASAP while getting Creeping Death to Level 2 so that I can use it for quickly taking out larger numbers of creeps in the jungle. Getting Children of the Grave whenever available. Always get 1 point at least into Siphon of Destruction AFTER Children of the Grave so that you can finish off those very low hp champs, because we ALL hate when they get away with like 12 HP.

Always start at golems, try to have someone leash them if you can. Smite the first golem when it's at smite-able health. You should be level 2 after this. Walk to the wraith camp and target the blue Wraith with your Mace of Spades and activate Creeping Death when you're about to hit the blue wraith. Walk across mid lane to the wolves and do the same thing. Walk through the river to the enemy golems and kill them, then the enemy wraiths. By then your jungle should have most of the things you killed back. So backtrack to your wolves, then Wraiths, golems. After that get Red buff and go gank. Recall, then go back to your jungle. Try repeating this path some but adding in Red Buff and Blue Buff when you pass them. Just keep doing this while ganking until you're level 10-14 and have the Giant's belt towards your Warmog's at least. If you did all this successfully you should be set for the rest of the game.

If there is an enemy jungler just use this route.
Golems, Wraiths, Wolves, Red/Blue(Whichever you want), gank, recall, wraiths, wolves, golems, red/blue(Whichever). Just follow that pattern and such and you should still be pretty good.

If all goes well you should have a score at least of 6+/6-/12+. Yes, you will get more assists than kills usually. Just always make sure you have someone you can either trust to solo, or someone who you hope can solo. Ganking might be a bit tough early on but it gets easier the further you go. Mordekaiser is nice early game and OP late game. The only person I've ever seen actually out-jungle me was a Warwick and that's because I messed up with some of my ganks.

Also, I'd like to thank everyone who reads this for reading it. :D
Oh, and sorry I forgot to add in health pots at the start >.< Try getting 5 with that nice cloth armor :P