“Put all your eggs in one basket” means “to put all your efforts or all your resources into one plan or one course of action”.
Usage in a movie (“Forget Me Not”):
– Yes, but there is another place you might like even better.
– I’m happy here!
– Please, Nan. Try. And remember, you always said to me not to put all my eggs in one basket.
– How absurd! I said nothing of the sort! What does that even mean?