You seem to be off to a good start. I would recommend reading up on the "rule of thirds" and the "exposure triangle". Understanding those two concepts will help you alot. Also, there are a few "sticky" threads at the top of the beginner's forum that have links to really good articles.
Here's what I saw in your photos:
#1: The horizon needs to be leveled. Otherwise, I like this shot. The reason it's grainy is because the ISO is too high. You would have to be in manual or one of the semi-manual modes (Av, Tv, Program) in order to set it yourself.
#2: There's motion blur. Whenever taking dusk pictures like this, I suggest bringing a tripod. It's almost impossible to get sharp pictures without one. You can raise the ISO to get a better shutter speed, but your pictures will be grainier. You can also buy a "fast" lens (one with a maximum aperture lower than f/2.8) which will allow faster shutter speeds with the same ISO setting.
#3: I really like this shot, but the horizon being in the middle kills it. Crop out have of the dead ground space and I think this one will be much better. I'd show you, but you don't allow people to do edits of your photos
#4: Again, there's some motion blur. Not as bad, but it's still there. Tripod, tripod, tripod.
#5: Here's another really good shot. I like the silhouette of the palm trees and the people on the beach. But there's that horizon, smack dab in the middle of the picture again. Cropping out a good portion of the sand will help this picture shine. I'd crop it just above the bird that's on the far left of the beach.
#6: You're dog's cute, but the picture is lacking. I'm not trying to be harsh, but there's a lot going against this photo. The on camera flash is useless in *most* cases. Since you can't control the intensity, you get the harsh highlights and shadows that we see in the picture. It just doesn't look natural.
Like you mentioned, black animals are hard to photograph properly. But there's some things you can do to make it easier:
-Lighting indoors sucks for the most part. Take the picture outdoors in the early morning or evening (when the sun's right above you, you get harsh light and shadows).
-Make sure the background is a lighter color so the dog doesn't get lost in it.
-Get down on the dog's level. It makes the picture look less like a snapshot.
-Have the dog facing towards the sun so their face is lit.
-Focus on the eyes. If there's a good amount of light, set the aperture to a higher number (called "stepping down" the aperture) like f/8 or f/11. That will make sure more of the dog is in focus.
Sometimes the comments on the forum are frank and border on rude. Just take them with a grain of salt. Most of the people here are very helpful, but they don't try to sugar coat it, either. Sugar coating what's wrong doesn't help anyone, lol. You're off to a great start. Keep shooting and posting!