After reading about the benefits of reciting Ayatul Kursi (ex. after every obligatory prayer) I was wondering if those narrations refer only to verse 255 of Surah Al Baqara or if they refer to 255-257 (three verses). Would reciting only 255 be sufficient if one seeks to receive certain benefits mentioned in narrations?

There are differences of opinion on whether it should be just Ayah 255 or include the two other Ayat. Ayatollah Sistani Says for the sake of precaution one should recite all three. Unless one refers to someone else in this matter.