Before of all, sorry for my bad english.

Well, I´m doing this build with Mordekaiser because the other that I´ve seen dont convince me of playing with Morde, and this one that I use, has shown me that is very useful, not only for making a lot of damage, even for going in a tanky way and tank a turret and starting a teamfight, you would be very hard to kill with that health regeneration and your passive, Mordekaiser can be more dangerous that most of the people think.

I can give you some tips starting the game with Morde, don´t focus on killing your enemy, is better to be in the middle of his minions and don´t let him to get closer and trying to hit him with your E. Also, DONT chase your enemy with a turret near at the early game, it would cost you a death and you would give 300g to the other champ, be careful but agressive at the same time.

Ghost will not only help you escaping of your enemies, it can be also a good "friend" to stalk someone and kill him, because if you are against a Teemo, or other champ that can run faster than you (not very difficult, Mordekaiser is a bit slow) you would need it to finish him and get his soul, or only the gold.

Ignite, you are going to use it in combo with your ulti, when the objetive is with low health, you could not kill it with the damage of your ulti, you probably will need ignite, to finish it faster. It´s very useful not only 1vs1 or 2vs2 or whatever, it would be very useful in a teamfight, because focusing in someone, you can kill him very fast and get his ghost to be a 6vs4 (If you can, take the ghost of their carry).

As many of the builds you can find here of Mordekaiser, you have to focus on E, because it doesn´t only do a good damage, is the ability that cna give you more passive shield of all, only hitting one or two minions.

After finishing leveling your E, go and focus on your Q, and dont forget to put the point of the ultimate, it would sound stupid, but you can make a mistake that will cost you a turret or even the game.

That is the order that I prefer to buy with morder, to go a little tanky, but very offensive too. The hextech is more for gettin some life steal of your skills, you probably wouldn´t need it with the Force of Nature and the Randuin, you can buy the Abyssal Scepter if you want more AP and magic resist.