You don't have to - тебе не нужно you'd better - лучше бы ты

"you'd better" it means what I think you must do.It usually uses in rude context. Example: лучше бы ты помог мне, чем ходить в кино. = You'd better to help me than go to the cinema. When you did something stupied or not so important for another person. But "would rather" = лучше бы,too. It what you want to do and what do you prefer to do. I would rather help you than go to the cinema. = Я лучше бы помог тебе, чем пошел в кино.

Вы не должны ..."" лучше