I have not included pots and wards down to the fact It is completely personal on the team and how you are doing. But Personally I like to have atleast 1 pot on me the whole time. Atleast until WOA. Obviously some of the items may have to be replaced with items such as force of nature, Or abyssal scepter. Although you wont really need those items since Rylai's and your shield is useually enough to keep you alive throughout team fights.

Farming as mordekaiser is generally pretty easy. Since you grab Hextec reveolver early on it allows you to be able to free use spells to assure last hitting. On the topic of wraiths. I will useually grab wraiths as often as possible, But only once I have boots of speed or higher. If you push dead to the tower you can useually safely grab the enemies wraiths and your own before returning to midlane and farming again. Because of your shield you shouldn't be afraid to get near the tower to grab a few extra minions, Since when your shield is full you can useually tank up to two or more tower hits, Depending on your level. I find mordekaiser to be one of the champions that you really have to try farming the whole way through the game even if its just picking up some wraith's or wolfs. Always try to go to lanes getting pushed by enemy minions to pick up as much farm as you can.

Mordekaiser is a very unagile champion and will take some pratice getting used to ganking with him. It will usually be best to go gank top, Since they will usually have a stun / slow. And It is always best to get as far behind the enemy target to assure a kill. When a jungler. Or someone from another lane comes to gank you; You will be able to blow them up very quickly but unless there is a stun. Or your enemy is in a very bad position a flash will useally be required to get the kill. These only apply early game once you get rylai's crystal scepter.
When getting ganked You will useually be tanky enough to escape without any worry. Unless you are serverly caught out of position. But as long as you have your ulti and ignite up you should be able to tank the someone with you.

Mordekaiser is an excellent champion for beginners, He is very simple yet incredibly strong. But if you are of a more advanced skill level you will find that he is rather complex.
Mordekaiser will be outranged by most other champions in mid lane. But with his sheild he is able to walk straight up to the minions and farm without worry. And once he has his hextec gunblade will be able to harass the enemy mid rather easily with a combination of well timed and placed skills. In team fight he can very easily go 1vs5 As long as he is not stunned or silenced etc. Sadly thats very rare