Garden leave
On leave because he/she becomes unwanted to the company

Get a life
Complain someone that he/she is too serious.

Get in someone's hair            
Bother someone

Get off someone's back          
Stop bothering someone

Get up on the wrong side of bed
Get up with a bad temper

Get the ball rolling
To get something start such as plan / project

Give the best shot
Try the best

Get somone's nerve
Bother someone

Green
New / Beginner

Give one's a cold shoulder
Treat someone in a cold way. Careless.

Give up the ghost
Die

Go Dutch
Pay the bill equally (usually with food)

Go fly a kite
Tell someone to go away

Go for it
Agree with it / Do it

Go native
Act the same way as local people.

Go south
Worse

Go over one's head
Something that is too difficult or not intersting at all

Grey area
Unclear area