To know your onions- знать своё дело, отлично разбираться в чём-л
When it comes to the cars,he really knows his onions.
To buy a lemon — купить что-то плохое по качеству
The people who had a new gadget have bought a lemon.
To put all your eggs in one basket-поставить все на одну карту,рискнуть всем
He lost his money because he had put all his eggs in one basket.
A big cheese-важная персона, большой начальник
His father is a big cheese in one of the international companies.
Bread and butter-средства к существованию, заработок
Teaching English is her bread and butter.