How can i make my quince cheap with using alot of cheap stuff?

well i really want one but my mom dont want me to have one beacuse it cost a lot and she makes good money compared what she did but i am wondering like Cheap! ballrooms out Side I Could have it . I live in MN im thinking to have it In Mlps Or some where in burnsville MN. there would be about like 300 people there im guessing an we would buy food my dress limo and A DJ i just really want one and i been begging forever and she does not budge . and i told her i only turn 15 once. please HELP!! (