For example, many people will encourage you to invest in a quality bed and mattress. Healthy sleep is important because it provides the foundation and energy for how we spend our days. This seems like wise advice. Buying a quality bed is an investment into my life.
Additionally, I would argue that healthy food, quality running shoes, and opportunities to learn are also smart investments. They may cost a little bit more, but they improve our quality of life providing valuable returns. Some might include travel on the list—I tend to agree so long as experiencing and learning from new cultures accompanies it.