The Australian-born newcomer - who only graduated from drama school a year ago - will be introduced to movie audiences as golfer Jordan Baker in Baz Luhrmann's adaptation of the famed F Scott Fitzgerald novel.
Debicki told The West Australian: "I probably spend more time with Carey [Mulligan] really than anyone else.
"She's just the most beautiful girl, she's a lovely, lovely person and I feel so lucky that on my first job I got to work with such a lovely cast."
When Debicki was asked how she prepared for an on-screen kiss with Tobey Maguire, she quipped: "[By] brushing my teeth."
She further explained that kissing a co-star is "just another thing you have to do. It kind of becomes as technical as how to open a door, really."
The Great Gatsby is due to open in cinemas on Christmas Day, 2012.
> Baz Luhrmann injured on 'Great Gatsby' set
Watch Carey Mulligan telling Digital Spy about her role in The Great Gatsby below: