Short term only new paint and a thorough cleaning are likely to boost value more than the cost, but joy and satisfaction have value, too.
Is the change likely to make you happy also likely to make you money?
Want a library of answers to the title question? Do a google search for “best home upgrades to increase value” … then search again replacing “upgrades” with updates, improvements, projects, and/or renovations.
Dozens of articles are published every year on this issue. The most informative article I found in a recent search was published in an old favorite Consumer Reports entitled 8 Ways to Boost You Home Value. This is a very extensive article with numerous links to additional information and articles on related issues.
In recent times the recommendations in such articles have had an increasing focus on technology. For older homes, the really good news is that most of the new technology is wireless. Place the component where you want it, then go to your smartphone to connect it where needed to function.
Updates and renovation are very nice, but don’t overlook ongoing maintenance and upkeep. “Pride of ownership” is an old idea, but a very real part of a satisfying lifestyle for most people.