Okay a few pointers to get you going:
The second set of cat pictures are not bad, because you've got down on its level, but the head-on flash has created some unsightly bright reflections from its coat and has it squinting in one. Try using natural light from a window and avoiding the onboard flash until you can pick up a decent flash and reflectors.
With the close up plant images, be careful with exposure because your camera has underexposed the first leafy shot quite a lot. Auto exposure can be helpful, but a bright background can leave your subject underexposed (and vice versa). Experiment with exposure compensation to overcome the camera metering's mistakes. Also, with these close up plant/flower shots be aware of the rest of the shot and be careful that it doesn't distract from the subject with stems crossing over or behind it. Planning your shots can make for a much better result later on! Sometimes you can doctor the scene a bit to help by holding stray plants out of shot (just don't wreck someone's flower bed!). Adding a bit of contrast in postprocessing would help with some of the shots which look a bit flat.
Good start, you'll be improving all the time if you are always thinking about your shots as you take them