Armor and lethality/pen
I am not really sure how to phrase my question but I will try. I have recently started playing jungle again and one thing I noticed is the difference in base stats and mainly armor. Some champions like Akshan are nearly impossible to kill. Now I know some junglers like talon can struggle against even the slightest armor item from enemy but still. Both me and enemy Akshan are fed and same levels. I have 2 items as Kayn while he didn't have armor boots and edge of night and do 0 dmg.
My question is when should I prioritise getting armor penetration from items like serylda, ldr etc. Should I switch up my build path order depending on matchups. I am more familiar with other roles itemisation and don't really get the assassins builds.