No need to struggle with color saturation, contrast or sharpness tools. These sometimes produce a very artificial appearance that is unattractive and looks amateurish. Using only the 'levels' feature can significantly improve the quality of your photographic image.
Of course, the quality of the original photograph is important, but you already knew that. However, sometimes an excellent photograph lies hidden within the digital image and that is where digital enhancement software plays an important role. I exclusively use paint.net but you will find that on other programs, the levels function works similarly.
Even if you use nothing else, you should know how to use 'levels'.