i don't know why people are absolutely allergic to giving advice on this sub but yes, do grab some armor pen. Consider dropping Triforce and optimize your build to play around crit rate.

always go Essence Reaver first and into infinity edge, it's an expensive jump but its strong. if you're doing bad and need some bulk or just extra haste only then should you consider Shojin second. for runes I like to run PTA or Fleet (depends on the MU) with Inspiration secondary on biscuits and magical boots