Change flooring to be more uniform
Also one of the more expensive upgrades you can do but it can have a huge impact. If you have old stained carpets mixed with vinyl flooring try updating to a laminate floor throughout. Generally people like to see all of your main floor living spaces in a hard surface flooring not carpet. Laminate or engineered hardwood especially in a wider plank look (at least 5" wide) will update the entire look of your home.