well this is a good question..........
the most important thing she wishes for is for the death of King duncan so she can be QUEEN and her husband can be king
and also after reading the letter she talks abt the murder and talks abt how she wants the spirits to take her feminity away frm her(this is a really important part). she wishes to be a man so that she could feel more confident in herself even though she is already sooo ambitious, and thus she says that if she were a man she can carry out the murder without any second thoughts.
this part after reading the letter reveals the most cruel side and the most ambitious side of LADY MACBETH
so basciclly all of her wishes revolve around the murder of king ducan
hope u found this info. valuable!!!!!!!! :)