You probably mean "better off" which means "in a better or more prosperous condition".
E.g. I would be better off with a new car.
She was better off in her old job.
There are a couple of other phrases:
"think better of"="to change one's mind about something".
E.g. She almost bought an expensive dress, but then she thought better of it. (She didn't buy it after all)
or "get the better of"="win a victory over".
E.g. He turned away from her before his anger got the better of him.
There's also a more prosaic meaning for "better of" (I mean, not idiomatic or figurative) - 'in the dress shop she liked the black dress and the pink one, but she didn't have enough money for both, so she had to decide. She liked the black one the better of the two."