Window blinds are important as they serve both an aesthetic design look as well as a functional purpose. There are many different styles of blinds to choose from horizontal, vertical and even swing out models. You typically have a lot of colors to choose from and you also have different materials to choose from including wood, metal and vinyl. The functional purpose of blinds is primarily to let natural light in, or to prevent light from coming in as well as privacy. Different rooms may have different needs regarding light. Some people like their bedroom to be completely dark at night while others like some faint light to come through. Rooms with televisions may need more light prevention to prevent glare on the screen during the day.
Determining the number of windows and the dimensions of each window is the most important part in developing a budget for window blinds.
There are many different retail and online outlets that offer window blinds. Once you have determined the number of windows and the dimensions of each, start to develop a prioritized criteria over what features are most important for each rooms blinds.
As an example, you may have high windows where you want battery operated blinds in opening and closing them. Other rooms might have an upscale interior design so you want blinds to match with the quality of the rest of the room. Simple functionality over blocking out sun may be a priority in different rooms.
Here is a great video from Blinds.com on how to select blinds.