r/oilpainting – question about Underpainting

I’m relatively new to Oils and everything I’m reading says I should be doing an underpainting first. I get working “thin to thick” and generally work that way but my few attempts at doing an underpainting have not turned out as well as when I just start painting on a blank canvas. I know there are really no “rules” but I’m curious how others are approaching their work and if I should spend some more time trying to work with an underpainting first. Thanks in advance

Self Portrait