Firstly, I think this is a direction worth going in and you are definitely developing.
Having said that I think this image has a lot of flaws.
If you want to create a realistic composite it helps to have a good source image where the lighting matches what is superimposed.
Here the lighting in the two photos is wildly different and the result looks highly unrealistic. It's clear that in the background image the light falls off in the foreground.
But perhaps the biggest problem in this image is the photo of the model. The skin colour is a massacre. Her face has a magenta colour cast. Her right shoulder is going into green, there is a massive and very odd stripe of magenta-blue on her left haunch and a purplish smudge inside her right thigh. The result is very nasty and makes me wonder: is this a model or a reanimated corpse?
You need to train your eyes to see skin tone and learn to use the selective colour tool in photoshop.