1st rule. have fun
2ed rule. do not engage jax late game by self or in death realm.
3rd rule. your passive is a godsend. use it to capture objectives.
4th rule. hitting your q on single targets are great and do best damage.
5th rule. use the w right before taking big hits, too soon and you haven't saved enough shield. use in lane for constant health regen.
6th rule. combo at right time. the q and e can and should be used at almost same time. practise makes perfect on this one. use correctly and can onebang entier minion wave(excepting cannons.)
7th rule. single hit damage buff does work on cannon minions so use it.
8th rule. spam spam spam spam spam spam spam spa... you get the jist. you have 0 mana cost. this allows for some ability spam. after riftmaker you will have smaller cooldowns. and will be able to SPAM MORE.
9th rule. is that these are a work in progress. will hopefully add more.
10th rule. DO NOT TALK ABOUT FIGHT CLUB.

there is a fine line of tank and mage. most of these items look like mage items. they also build health.just go with the build.

never build tank items on morde. the spirit visage is there cause of the passive, and the passive works well with morde w and the lifesteal. that is why it is the last item.

in order of abilities you should get q, e, w. level ult when you can. ult is useful in teamfight cause of single targeting. you can cast e right in front of you to push enemies backwards.use ult on squishy champs then q and e them to death. figure out what comes next after you leave ult.