Do you want to make your house look great without spending a lot of money? Windows are a great place to start. There are many inexpensive ways to accentuate and ornament your windows, for example fabric panels. These look elegant and it's easy to find a variety of affordable fabrics that match the look and feel of your room. Box valances are another way to get that designer look and you can even construct them yourself with a little creativity. Adding pillows and a throw to your couch are less expensive than reupholstering and give your living room a modern, plush feel. Ottomans too are great decorative and functional pieces, but they can often be quite costly. Try purchasing a nice fabric and turning it into a slipcover for a crate. Your ottoman will look great at a price that's no where near what you would pay in a furniture store.
Also consider adding decorative moldings to your home, they cost less than wood and add a little visual interest. Finally, consider spending money where people will see it. A vase may not be the best use of $100, but luxurious floor to ceiling drapes are.