You would usually say "don't even bother" or don't bother trying". It means that even if you put forth your best effort you will not receive the desired result. Example - You tell a friend you will apply for a job. He tells you : "Oh, don't even bother." You ask : "Why not?" He replies: "I heard the boss is going to hire his cousin - no matter who applies." You reply : " Ok. So it's not worth my time." He replies : "Yes."

It means "don't do it". Usually because it's not worth the effort. Or the other person doesn't need or want the action.

Thank you all, all are revealing to me!

It is an unfinished idea Dont bother doing IT. IT is not worth doing. IT is futil. IT would not pay off if you did it.