Out of this world = extremely enjoyable or impressive.

• What a restaurant, the food was out of this world!
• The performance was out of this world!
• This bakery sells some out-of-this-world desserts.

Like gold dust = something very difficult to get because a lot of people want it.

• Tickets for the concert are like gold dust.
• You can’t get those new trainers anywhere. They’re like gold dust.

Leave a lot to be desired = be highly unsatisfactory.

• Apparently, her cooking leaves a lot to be desired.
• I’m sorry to have to fire you, Mary, but your work leaves a lot to desired.

The lesser of two evils = The less unpleasant of two choices, neither of which is good.

• People voted for him as the lesser of two evils.
  (i.e here both the candidates are unsatisfactory with slight difference)
• I was offered the post either as a typist or office clerk. Aptitude-wise both the jobs didn’t satisfy me, but I chose the post of a typist as the lesser two evils.