lets start with her debut single "I kissed a girl" spent 7 weeks at #1 and its certified 9X platinum (close to diamond) its a classic that is still remembered today.
With her debut album "One of the boys" she got 3 top 10 hits, I Kissed a girl (#1), Hot n cold (#3), waking up in vegas (#9), the album has spent 92 weeks on chart and has sold over 10M copies WW.
let's move on to her sophomore album "Teenage Dream", she scored 5 #1 hits from this album (6 with the complete confection), she became the second artist (tying Michael Jackson) and the first female artist in HISTORY to achieve this, its one of the best selling pop eras ever.
All the singles from "Teenage dream" were top 3 on the Hot 100 and every single is a classic that is still remembered to this day.
with her 3rd album "PRISM" she scored 2 DIAMOND singles (Roar and Dark Horse) becoming the only artist to achieve this.