Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
Mordekaiser is arguably the best farmer in LoL due to his low cd nukes. Someone might say these items are fairly pricy, but if you aren't averaging 180-250 minion kills a game...then you aren't playing him right.
This guide focuses on great damage output, above average health and mitigation, and around 290 health regen. per 5 endgame. You WILL get these items if you're a good farmer basically every game.
Note: I recommend getting 6 health potions out of the gate. Reason being you can literally stay out FOREVER with mordekaiser, and never miss out on any exp or gold. Also, if your health is kinda low, and you have no immediate need for your ult, pop it on someone just so you dont have to recall and heal. Also the Lizard buff works amazing with mordekaiser, grab it every time you can.
Feel free to comment, I'm always open for suggestions :)