I am doing my PPL as well at the same time as trying to get into cadet programs. I am pretty sure it won't hurt your resume saying that your doing the PPL theoretics. It's not expensive (few 100 euro's and probably you will be able to get them cheaper second hand somewhere) and not to difficult. For me it is a nice warm up for what is to come in the ATPL. You don't have to know and remember everything in there but it will give you some basic knowledge on a lot of the subjects of the ATPL theoretics. If it is appreciated by the interviewers, even better.
I am studying the BAFA-books.