Nothing is ever fool proof, so instead of partitioning your box, why not just get a VMware program and install that on your system then install Kali. This way, during your learning, if you happen to make a mistake, you just delete that portion and create it again, and still be able to use your laptop.
My laptop has Ubuntu on it, and in VMware, I also have another Ubuntu that I can mess with and not have to worry about messing up the laptop. I can try out scripts and other things and not worry about the system. You can also do this with Kali, which is a good program for pen testing.