HELP ME......Death Duet Event

PLEASE HELP ME 
I have brought 24 event packs for the death duet event and i didnt get the heirloom! I have spent all my Xmas money from my parents on this. What do i do!!!! Anyone please help. It says that im missing 6 epic and 2 legendary items. If i want to get the heirloom how many more packs do i need to buy?