For a beginner, badminton is a relatively low cost sport to start playing. If you want to buy your own equipment then you need to consider the racket and shuttles.
Racket: These are made of various lightweight materials. They come in many different makes and prices but If you are just starting the game you do not need to buy the most expensive racket. Buy a racket that suits you.
Shuttle: These are plastic or feathered. If you are just starting, plastic shuttles are ideal and cheaper. They come in three speeds - fast, medium and slow. Buy medium speed to start with until you know more about the game.