Its fun to play with...
Nothing wrong with playing around even if the results are "over the top".
The critical issue with any "realistic" photocomposite is the blending (i.e. ensuring that it does not look like a cutout pasted onto a background, good blending and above all, very careful attention to how the highlights and shadows are falling on the various elements (this includes showing the objects are anchored to the ground and not floating in the air). Get those things right and you end up with a powerful piece but if you get them wrong, the image just does not work.
Enjoy your project!
You need a shadow....
It might be a stronger image with the radial effect placed somewhere to the left, balanced by the car.
I too now think, what Rufus has suggested would work more
Anyway, immediately after asking my question of Rufus above, I am posting my latest effort in this work in progress. Quite like the old fashioned petrol (gas) pumps, though not certain they are what I will end up with. The car now has a driver. The shadow of the car in not very good, so I will look at a few more video tutorials on the subject and get back to it. I have taken note of what you have said, Manfred, and have done a "merge visible" of all my layers, then have chosen a blend mode of "Soft Light" for the result.
The fuel pumps add some balance and the car now has an implied destination, but the pumps are floating a little when the image is enlarged.
My suggestion about moving the radial effect was simply to move its centre to the left...something like this perhaps?
Maybe crop a little from the top too to emaphasise a diagonal line that the pumps and car are on. But of course it depends on whether you have other items to add to the composite. And the central positioning of the radial efffect might be a critical part of what you envisage for the finished article.