The best person to help you is a local Realtor who knows the market, knows your home, and your personal situation (when you need to move, how much you expect to net when you sell, etc.).
For example, if most of the homes in your area are like yours (1950s ranch, clean, but not updated), then they can suggest options that will help you get the most for your home.
Here is an example of what not to do: I was asked by a seller to help them get their home sold when it failed to sell the first time. She had invested $6,000 in a new master bath. The bath looked great, but the real issues were that the home desperately need a kitchen update, new carpet, and paint. Had she invested the money in these more visible items, people never would have noticed the bath.
So it's not how much you spend, its where you spend it. Just because they always says the highest return is on bathrooms and kitchens, they are also the most expensive.