Beautiful light makes a space feel right. Where I live, the answer to all most interior issues between November and January is mood light. Bring more warm, dim, low-level light in your home and it will be instantly cozier.
In my home, three light sources in one space is the minimum. With eight, nine, ten lights in one room, things begin to feel right.
You do not need a huge budget to make this happen though. Candles, oil lamps and lanterns are wonderful sources of mood light. They are also helpful in figuring out spots where you could possibly add an electric light in the future. Simply move lights around and see if your space has dead corners that would benefit from more light.
For a relaxed atmosphere, avoid bright overhead lighting. Instead, create pools of light where people like to sit and lounge. I think low floor lamps and lanterns are especially attractive. Just make sure there is proper task light available for reading and working.
Lighting candles and lamps on windowsills helps maximize the sense of space when it is dark outside. They mark the outlines of the space in a subtle, beautiful way. When inviting people over, I put on great music, chill the wine and light candles in every room. People and places tend to look their best in candlelight.