I use an old version (7.04) of Paint Shop Pro I bought around 10 years ago. I've looked at trial editions of the newer versions but they only seem to add stuff for digital photo editing (red eye removal etc), which I'm not into to any great extent.
It doesn't really matter which program you use, so long as it will support layers. It is more important that you know how to get the best out of your program's features. For instance how to draw various lines and shapes and what the settings for the airbrush tool do (density, opacity etc). Understanding the more advanced features like masks and filters is sometimes useful, but not really essential. If I was to invest in Photoshop it might do a slightly better job, but it would probably take me six months to learn how to use it as well as PSP.
