First let me say that that is a very loaded question!!! I’m not sure what room or rooms you have in mind. I give most of the credit for my ideas to HGTV as I am a HUGE fan of that channel, particularly Design on a Dime and Designed to Sell. They are favorite shows of mine.
I am a beginner and have had no schooling on decorating but it has recently become a passion of mine and I can make a few suggestions.
Sometimes just rearranging the furniture in your room and a fresh coat of paint can make all the difference. You can also move furniture pieces from one room to another. Work with pieces you already have. Wood furniture can be stripped, sanded and refinished. If your furniture has handles or knobs, you can purchase new handles and knobs to give it an updated look. If you sew (which unfortunately I do not and wish I did), you can make curtains and accent pillows relatively inexpensive. Candles, fresh flowers in a vase or a bowl of fruit are nice accents as well.
Don’t be hesitant to check out garage sales, swap meets and the dollar store. IKEA and Bed Bath and Beyond are also great stores but they are more expensive so be sure to check out their sales.
Keep in mind that you can do your room or room’s one step or piece at a time. It may take a little longer but you will be so happy when you are done.
Hope this has helped a little!! If you have any other questions, don’t think twice about asking.