20. Oxygen
Oxygen obviously allows humans to breathe, so we do need it. We also need proper oxygen levels so that we can actually breathe it in. However, we may not completely need a massive amount of oxygen on this new planet as it can be created too. If a planet has something known as cyanobacteria, this is a good thing too.
These help to produce oxygen and were among the first things that Earth used to make the oxygen it needed. While the overall number would be too high if a planet had a lot of this around, it could be useful to the long-term health of the planet and humans alike to have them. You often see cyanobacteria described as blue-green algae, which allows us to find it easier.