It may be a general answer, but school is only a small part of life and your course of study only covers a fraction of a percent of the knowledge that exists in the world. Even look at how many courses you take divided by how many courses a university offers.
The best thing I can recommend is to research things you come across that you are interested in and could be practical.
If you are looking for suggestions:
- Financial basics like time-value-of-money (inflation, interest, etc), opportunity cost, investment vehicles (bank account, CD, stocks, bonds, options, etc)
- Mechanical skills such as changing a car's oil, fix a leaky faucet, replace a toilet, etc. This is stuff that you can look up when the need arises. The point here is not to write yourself off before trying. Start with small projects.