How you choose to number the course depends on the material in the specific course, and whether they are semester or quarter length courses. The ** degree I linked from Cal State LA includes 5 general physics courses, 1 quarter each. So, along the same lines, with one quarter courses, and using Cal State LA as a template, here is what I would say:

Physics: 20 classes

Physics 201-205 (general physics)

Physics 306 (modern physics)

Physics 311 (elements of modern astronomy)

Physics 410A-B (mathematical methods of physics)

Physics 411 (introduction to astrophysics)

Physics 425A-B (introductory theoretical physics)

Physics 426A-B (Electricity and magnetism)

Physics 427 (thermodynamics)

Physics 428 (statistical mechanics)

Physics 432A-B (introductory quantum mechanics)

Physics 444 (nuclear physics)

Physics 488 (modern topics in general relativity)

*Physics 306 includes special relativity, as well as introduction to atomic physics*.

Mathematics: 6 classes

Math 102 (college algebra)

Math 103 (algebra & trigonometry)

Math 206-209 (general calculus)

*The math department has specialized course in linear algebra, differential equations, vector & tensor analysis, differential geometry & etc., all of which are required topics, but all of which are covered in the physics department mathematical methods courses.*
I would add to all that one additional special course each in special & general relativity, as both of the courses shown here are general, survey courses. Neither is an in-depth study of the topic, but that is what you really need to appreciate gravity at an advanced level, perhaps something like the Caltech course I pointed to earlier,

Physics 236 (General Relativity) and

Physics 237 (Gravitational Waves). Furthermore, a class like Caltech's Physics 229 (advanced mathematical methods of physics) is really good for advanced topics in general relativity.

I also note that this set lacks in depth study of topics specific to astrophysics & cosmology. So one might supplement this list with a few classes from, say the

Caltech astrophysics course list. Topics like galaxy formation or cosmology would be good supplements to a list like mine.

Well, there you have it. I think this is a good example of what you need to know of you want to understand gravity and the applications of gravity, at a reasonably advanced level. But there is no substitute for experience, and I would say that a

*real* advanced understanding would take a course list like this, plus 10 years or so of experience. After all, in the real world, a PhD is not where you stop, it's the goal you have to achieve in order to get a start on a career in the field.