Personally, I love Mord's kit. I LOVE it, and that's why I main him.
I also understand that Morde has terrible base resistances, movespeed, hp, and attack speed. He is also item reliant.
As a result, I focus mobility by using ghost/flash, or more recently ghost/ignite. I like to throw in Ludens for obvious reasons. I mean really, noone expects a mobile Mord. I also take gold income masteries as like I said, Mord is item reliant and needs gold.
Since my summoner spells give me potential to stick and have kill potential, I favor Ionian boots unless I must build diffrent ones. Use spells faster, and have more CDR on abilities to keep shields up.
Hyper focus cs
Poke them down and only all in when they are low or you can safely get fed adc ghost for a killing spree
WARD, MORDE TAUGHT ME THE IMPORTANCE OF WARDING
Time your heals as w can be deactivated
Build defensive offensive items like Zhonyas, Abysmal, Mercurial, and Maw(situationally).. Ya gotta look to see who the biggest threat is, counter build them so you can deal damage and sustain theu thier damage, so you can get a super fed ghost, get kills, and more importantly SEIZE TOWERS
If you have a ghost, take objectives and turn fights around. Objectives OP tho, and the cs from pushing lane to get to the towers outweighs a few kills
High AP=more heals and a powerful ult melt
High AD=sustained damage and bursty Q, and ghosts that HURT. You need some hp to stay alive tho if you want high AD, as your w and ult will be weak
I tend to lean towards a hybrid build, typically heavy on AP
Dragon ghost=you best take as many objectives as possible, you are DRAGON SEIGE MORDEKAISER
Boots start is a good way to sustain lane and make up for low mobility. Start against skillshots
Amp tome start against squishies
Long sword for medium pot sustain and help last hitting early
Mejias is OP on him if you know how to play him well, DON'T DIE
It's okay to up a mid game, for poke and bigger shields early, just have hp to mitigate the high hp costs of spamming it(maxed e first against vaybe as adc Mord, and she couldn't play against me)
If the poke is too much, max w first for sustain.
Learn to poke with w deactivate as they cs. Cast on a minion and deactivate when they are in the circle, even if the 2 circles don't touch.
Ignite helps