One of the best ways to find an answer to a question like this is to research sites that specialize in business, finance, management, and related topics, and peruse lists that breakdown essential managerial skills. Not all experts completely agree on the most essential skills a manager needs to possess, but there is enough consensus to form a composite picture.
CNN Money lists five skills essential to managers. First is honesty. Transparency between managers and employees engenders trust, which leads to more efficient performance. Second is diplomacy, which means the ability to mediate conflicts through mutual respect and compromise. Third is time management. It is essential that managers have the ability to focus employee efforts on top priority tasks. Fourth is delegation, which means passing on responsibilities and tasks to others so that managers can perform their primary function of oversight. Fifth is team-building: the ability to create, develop, and motivate teams that can work well together towards common goals.
The Brighton School of Business and Management lists six crucial managerial skills. First is the ability to communicate efficiently with the people they manage. Second is good organizational skills. Third is the ability to build teams, as mentioned above. Fourth is leadership in general, which is defined as the ability to set goals and assign responsibilities. Fifth is the ability to efficiently deal with changes. Sixth is domain knowledge, which refers to an overview or understanding of the process or area that they manage.
CEO Magazine lists 10 important management skills. First is integrity, which is the same as honesty, as listed above. Second is team building, which we can see made all three lists. Third is positivity, or maintaining a positive attitude. Fourth is efficient communication, as noted above. Fifth is the ability to be an effective listener. Sixth is emotional intelligence, which refers to the ability not only to understand and control their own emotions, but also to empathize with what the people under them are going through. Seventh is delegation, which is mentioned above. Eighth is the ability to make decisions quickly if needed. Ninth is collaboration, which refers to working with others rather than attempting to go it alone. Tenth is flexibility, or adaptability.
We can see, then, that the most important skills that are essential for managers to cultivate appear more than once in these lists. These skills would include honesty, delegation, team building, communication, and organization.