I think the most significant points to underline are these.
#1. Keep your background just that. A background. You did this well in pictures 2 (1484) and 4 (1608). They’re simple and not distracting.
#2. Keep your hand steady and you shutter speed high enough. Did you notice some blurriness in the first picture (1481) as well as in the 2nd (1485) and 5th (1608)? Your shutter speeds in those pictures are fairly slow (none faster than 1/80th) Learn about shutter speed here, here. and here
#3. Finally, experiment with eye-level perspective. In all the shots except the last (1608), you’re either not quite, or not at all, at eye-level with the dog. When I look at those pictures, I feel no sense of “connection” to the dog. The first three almost look like accidental shots; the dog was walking past, and someone happened to bump the shutter button.
But that last shot is great. (expect for that motion blur.) The dog’s eyes – the life of the picture – are visible and shining brightly. This picture, alone of the five, connects me to the dog, because of the eye-level composition. The dog itself is just bright enough for me to appreciate the texture of the fur, but not so bright it looks like an apparition. The background is complimentary and simple.
You can find some great pictures of dogs at this website and glean ideas.
Hope this helps,
William.