ok....
don't get me wrong but these are not "great". that's a strong word to use here and implies that you know much more then it's showed here... that being said here are my thoughts
- watch for the bg
- learn to recognize influence of the light
- learn a bit about composition, angles
#1 & #3 look nice for me, although to be fair, with a 50mm 1.8g you can do better. Why don't you try out a little more of a lower angle on the flower shots? The 1st one would have looked even better had the camera been at the same level the flower is. In the picture, the camera is just a bit above the flower, angled downward. The same goes for the last shot, which I feel would have looked better if you'd taken it at or near the ground level.
Most important thing to remember is that there's no right way of doing this, try out different things and see what works for you. Good luck