Is fully assembled furniture worth it for apartment living?

I didn't realize this until after moving, but an empty living room can really affect your mood. Not empty in a I haven't decorated yet way. More like, every time I come home, it feels like I'm living in a temporary space. The sofa was bought in a rush, I still haven't picked a coffee table, and the TV is sitting on a random stand. The whole room just doesn't have a real focal point. I want to redo the living room, but I don't want to keep buying random pieces one by one. I'm leaning more toward finding pieces that already work together in terms of color, material, and proportions. Something warm and modern, maybe a sofa and TV stand combo that at least gives the room a more home feeling first. What do you think makes a living room feel warmer the fastest? A sofa, lighting, a rug, or a TV stand?