The most common Chinese ways of saying Happy New Year are Gong Xi Fa Cai (Mandarin) and Gong Hey Fat Choy (Cantonese). Even though the pronunciations are a little different, both are written the same way.
Gong Xi is congratulations or respectfully wishing one joy.
Fa Cai is to become rich or to make money.
Thus, Gong Xi Fa Cai means wishing you to be prosperous in the coming year.