Hail of Blades - Fast Q
Taste of Blood - Healing stuff with E
Eveball Collection - Best Pick from the 3 for Morde in my opinion
Ravenous Hunter - Extra Healing with QWER AA that fusing with Gunblade
Nimbus Cloak - After using R you need this speed to get close to enemy and end him up
Scorch - Cancer the lane of the enemy and Bonus overtime damage to your R
Domination + Sorcery - Simply more AP = Win

Pros

-Massive Early Game Damage
-Can take Dragon pet at lvl 6
-Great Self healing
-His W saving Teammates with the heal it does
-He Can Rush In 3v1s and even 5v1 if he have the right healing items
-Ultimate Can Slow + Burn for 10 Seconds with Liandry's + Rylai's - that means CANCER
-EXP Bonus near allies

Cons

-Low Movement Speed
-Low Attack Speed
-No Crowd Control Abilities
-If no allies or minions nearby, his W becoming weaker
-Abilities Cost Health
-If you don't kill your enemy in the first 10 seconds after using R on him, you lost your pet
-If stucked in cooldowns and stucked by hard CC both, he ****ed up
-Big size body so it's pretty easier to shot him with Skillshots

Mordekaiser really good in teamworks, his dragon can bring the damage and slows behind while Morde himself standing in frontline with his W and starting to punish the enemies with E and Q, I recommending you to use your W on the lowest HP champion near you for try to save him with the healing, your job is focusing on the lowest champ of the enemies then rush on their tank with the pet of him/dragon pet.

A One Rule for Mordekaiser in late game:

JUST ONE SHOT PEOPLE WITH A SIMPLE R CLICK.