1) Just change the color of one wall. You do not need to change the color of all your walls. Just choose one wall to be an accent wall. It is a great way to add texture and depth to a room.
2) Try adding wall art, and other decor on the wall. It will add some texture and character to the room.
3) Try changing the layout of the furniture. Do not just get new furniture. It is amazing how you can breathe new life into a room by just moving the furniture around.
4.) Add some pillows or blankets.
5.) Add fresh flowers, or plants to make the room more homey.
6.) Add trinkets of little knick knacks to fill the corners of the room.
It is all about perception , even the smallest change can make a big impact on the overall appeal of the room. Interior design is all about perception, the moment you change even a small aspect of the entire existing setup you will feel a new energy in your home and will also help you generate new ideas to get more out of your existing interior design elements without spending more money.
Bottom line, do not stress out over it. Decorating your home should be a fun task. Just take one room at a time, and before your know it the whole house will be done!