Without a number of speakers you can not have a “surround sound”. When you are watching a movie, sounds go around the room. To become part of the movie, you need to place speakers around the room. You need to get the right speaker for the right application. There are plenty of choices out there for speakers. They could be floorstanding, bookshelf, satilite, inwall or inceiling. Some manufacturers even have speakers that are discrete which could appear to be part of the wall or disguised as a picture.
The home theatre setup need a number of speakers placed in the correct positions. 5.1 speaker set up is the most common setup. 7.1 is becoming more popular. A pair of front speakers, a centre, a pair of rear (or surrounds) speakers and a sub woofer ( the .1). To have a 7.1 set up you need and an additional pair of surround speakers. Now with the introduction of Dolby Atmos, you could have up to 11 speakers and 2 sub woofers.
Pictured below are two popular brands, KEF and Jamo speakers.
How far you go with your home theatre is up to you. Five, seven or thirteen, get enough to suite the room.