When I read "good DOF" I assumed you wanted it very deep, so you can take a closeup of a flower with the background mountains also in focus.
So it's shallow you want. I've not heard that ever called "good".
Here is the way to get a shallow DOF:
Use a longer focal length lens. Look for something at least 85mm.
Use a wider aperture. Look for a lens with a wide maximum aperture, say; f 1:1.8.
Separate the subject and the camera from the background. (back yourself away from the subject)
In your price range, I recommend the Nikkor 85mm 1:1.8, but you'll have to find a used one to fit your budget.
You're welcome.