Primered car, needs fixing, and then what.

Your paint is never going to be any better than the prep work. When you think you are done sand for about two more days.

As for the HF gun, I have painted three cars with them, the first I had results similar to yours. Then I read the instructions and spent a lot more time sanding for the next one. Much better results. I would not throw money at better equipment until I got what I thought was the best possible result with what I have.

Practice on scrap or something, practice makes perfect.

This was my third paint job. Pic was taken about 6 months later after the car got driven over one of those rocks on the edge of the drive behind the car.