This article is a good starting point: [https://www.houzz.com/magazine/how-to-make-your-living-room-look-bigger-stsetivw-vs~72094888[(https://www.houzz.com/magazine/how-to-make-your-living-room-look-bigger-stsetivw-vs~72094888)

I'm a believer in using really big mirrors to expand space. Houzz is misbehaving so I can't post this here, but it's a good example: [https://www.houzz.com/photos/south-london-apartment-contemporary-living-room-london-phvw-vp~16465808[(https://www.houzz.com/photos/south-london-apartment-contemporary-living-room-london-phvw-vp~16465808)

What are you working with? Generic responses may not fit your space. Pictures please.