You can improve your photos drastically just by editing them using basic editing functions! These are some that I have done, and I love looking at the differences between the before and after pictures.
This is my grandfather's dog, Cherokee, basking in the sun one afternoon. I couldn't get his face because it was partly cloudy, but I brightened up the picture so you can see all of his cute face!
My sister, cousins, and I on Christmas Eve. This picture was taken using my mom's phone. The colors were so dull so I used primarily saturation to bring them out some more with just a very very VERY slight hue change.
John and myself taken with my iPhone. The lighting in the room we were in was really weird and made our faces look dull. I brightened them up and slightly tinted the hue to bring some life to our faces.
Very easy and simple techniques that make a HUGE difference!!