Warning...
This build is if you only get fed at the start of the game.
Using this build if the other team is fed will usually mean you will die before doing any damage.

These runes are normal morde runes and even though you dont get fed should still help you early game. (Which is one of mordekaiser's downfalls)
Mordekaisers masteries are like all ohter ap casters.
Bringing ignite makes your ult much more powerful and health pots will not be as effective.
Flash is good because morde can quickly get to the enemy to burst down. Also so that if morde gets cc'ed or ganked he can flash escape.

You put your (e) siphone up first for the amazing damage poke it deals. I use this countless times to just slowly kill then use the rest of my burst to finish them.
Your (q) mace gets put up second when you have your sheen. If you dont have your sheen or you are not going to get it soon, put your (w) up for the armor.

Good
Awesome burst.
Ulting opposition adc and killing him will win you games and turrets.
Very good at farming and pushing lanes.
Passive gives him sheild

Bad
If silenced,stunned or most other cc while destroy morde because he cannot use his passive effectivly
Hard to win against fed opposition
Morde has no cc

Mordekaiser should be ether solo top or mid.
Try just poking with your (e) at the start, wait for your jungler to gank or flash in and burst down them.
You WILL need wards if u are solo top so you dont get shut down by their jungler.
Morde is a great farmer so as well as poking, try to use your (q) and (e) to farm.