Everyone always groans over Arithmancy because of the maths. It's not too arduous - and the maths may be the basis for the form, but it's more than just that. Theory, for one thing. And a good deal of comparative study. Challenging, but interesting. I was disappointed to give it up, in fact.

I think Ptolemy is in the NEWT-level course. You could ask him to show you his textbooks. I'd send you one of my old ones but of course, that's impossible at present.

Of course, the inclusion of Dark Arts is definitely an advantage for your generation, one the Lord Protector was eager to see given to you. If Professor Carrow believes you would do well at it, it would be foolish not to pursue them.