Q-Tentacle SMASH-is a must to max first. it gives you a passive first off. Tentacles that hit enemy champions HEAL illaoi for 5% of her missing health. So in short, the more hp your missing the more this will heal. Any tentacles that hit, not just q tentacle, your passive generates tentacles that work with W-Harsh Lesson,or by E-test of spirit turning into a vessel for tentacles spawned or R-Leap of Faith. so maxing q will also increase tentacle damage. the more damage done however does not heal for more. more damage on illaoi means more damage.(not like lifesteal).

Harsh Lesson W-this skill is pretty good when near a tentacle or when hitting a turret. definitely use when you can make good usage of your passive.

E-test of Spirit. this skill is the trickiest of them all. OK, so first skill shot. done. first enemy champion hit. will pull a spirit out. now depending on ratios and level of ability will amount how much damage is done to them. THIS SPELL CAN NOT KILL A CHAMPION because it only a % of damage is transferred to the host. If their fighting you fight the champion instead. if their running fight the spirit. we fight the champion becuase the more they damage you the shorter time you have to hit the spirit. spirit lasts 10 seconds. so lets say malzahar casts space aids on you. it will tick you for 4 seconds of damage. that means spirit will be reduced by 4 seconds while going down the 4 seconds of spell. malzahar space aids+spirit time=6 seconds to hit it. not including other sources. only the target champion fighting you can reduce the spell.
generally fighting the champion is best, when the run away, grab their spirit*e* and fight that. if someone comes to your lane to help gank *jungler or mid* it might be best to let them chase and you fight the spirit because you have 0 gap closers.

R-leap of faith very simple. more enemies hit=more tentacles. W has a 2 second cooldown so spam that ****. tentacles also swing 50% faster which is actually useful.

q can clear an entire wave almost, and if ahead with right stats will 1shot the wave. other than that it can be very rough but that's why we have the mastery Tough Skin. because you take a lot of damage that is really hard to notice from minions when trying to clear waves.

autoing a wave is ok but for some reason it does not feel right with illaoi.