When it comes to coffee at home, there is one single, most important improvement that stands above any other : grinding fresh. If you purchase your coffee pre-ground, you have a guarantee to lose flavor and quality. This is due to the loss of delicate aromatics in the minutes following the grinding of the beans.
This is true for any brew method. Whether pour-over, filter or espresso, your cup of coffee will be better if you grind fresh. In other words, grinding ahead of time is just like buying a nice bottle of wine or craft beer; and opening it at the till of the store. When you drink those later in the week, their quality will have decreased by a lot.