i use this build not to get kills but to help my teammates kill, also this build gets rid of towers by yourself. in this build u can 1v3, but only if there not fed. you can rush in and get out for a hit and run.

i would use "Heal" and "Flash"

Heal = Helps you and Teammates get out of sticky problems

Flash = get u out of harms way or hunt down a enemy

I choose armor penetration so other Rammus and big tanks wont be such a bother. I chose magic resist for the reason magical based attacks can not hurt you as much, and have less effect.
and armor for early game win. and the quintessential runes i chose move speed, because it helps a lot when 1v3ing people

the best way to play this Rammus is to farm when not in danger and when you got all the items, u pretty much kill in a blink of an eye. this Rammus build is too help win late game but might have trouble in early game until lvl 6, then you can 1v2,lvl 16 u can 1v3 and I usually win cuz they cant keep up. the first three items make Rammus over powered and the rest of them make him unstoppable then there is the last item which is your choice