Great thread and I see Kayty has you well in hand here. I agree that your drawing skill is very strong and this is a lovely little Corgi portrait.
Darker darks really add depth and dimension to a drawing, as well as light tones.
I often use a 2B as my darkest (softest) lead, but I get it darker by layering it with harder ones, HB and 6 or 7H. I'll set the tone with 2B, go over it like lasagna with HB and 7H, and go back again the same way if I think it needs it. I less frequently use 3 and 4B, and nothing darker than 5B and that only rarely.
Just as a by the by, notice how much depth your wooden pier has in it, as simple as it is, because of the high contrast of dark shadow and light wood. Also you didn't just draw a line to indicate the spaces between the planks, you made them actual shadows, which is another reason it works well.
You don't want to turn your pictures into cartoons by using too much dark and light, and this drawing is nice enough to leave as is, but you might experiment on future drawings with seeing how dark you can go, and widening your tonal range a bit.
don't worry, spiders, I keep house casually.
~ Kobayashi Issa
(1763 - 1827)