Idioms are an important part of spoken English, just as they are in any other language. You don't need to know all of them but certainly the knowledge of the basic idioms is necessary.
They spice up conversation and add beauty to the language. However, it is not advisable to use idioms frequently and unnecessarily just to show your knowledge of idioms.
1. Their director always talks down to them. [Here talk down means a person talking to others in a derogatory manner]
2. George is a bit of an odd-ball. [He is a strange person, describing weirdness or his actions and style which you find unusual]
3. I just ran the programme in front of you and still you didn't notice!
"I'm really sorry, I was miles away. [Saying miles away, the person says that his thoughts had wandered and he wasn't able to concentrate as his mind was away then]
4. Tilden is on Cloud Nine these days. His father has gifted him that car. [On Cloud Nine means extreme happiness, almost a situation of bliss]
5. My wife is just a bit under the weather. I guess she needs some rest or may be a pill but no need to go to the doctor. [When you say that you are a bit under the weather, you mean that the impact of weather has made you ill, or because of it you aren't exactly well]
6. The moment Robert made that comment about my writing skills, I knew he was trying to butter me up. [Praising excessively with an ulterior motive or a sycophantic nature]
7. That's Bob's habit. To pick holes in whatever I do. And I know it for long. [Criticising].
8. They charged us 50 bucks for that burger. It was a real rip-off. [You can also say when you are cheated or over-charged like 'The driver ripped us off'.
5. Camilla has a heart of gold. [Someone who is kind, generous, harbours no ill will for others]