I want to open my own miltipul banquet hall and I want to know how much should I have budget for this?

First its not a good idea to piggyback your question on someone else's. This can lead to confusion. You should start a new thread. So I've moved your question to its own thread.

What is a "miltipul" hall? Where are you planning on opening this?

We can't tell you how much without more info. But we can suggest some of the things you need to consider.

First is the physical hall itself. Are you going to build from scratch or purchase/lease a property? Second is the costs of construction/renovation to prepare the property for the intended purpose. Third, is marketing. Even before starting you need to do a study to see whether such a facility is needed and what it will earn. Then start working on getting bookings while construction goes on. You will also need to hire staff, get contracts for supplies etc.