Moray, it depends on what type of firearm you are building at the time. Lots of interesting tools can be made in your shop, versus buying them. I specialize in the AK series, and accordingly most of my homemade tools as well as storebought, are kind of centered on them. A drill press is a good investment in general when working on firearms, as is a tabletop lathe, if you can afford one. I can't and usually have to sub out my lathe work, like turning barrels. That's the first tool I would buy for my shop if I had the extra $$$$$. Good luck, and I hope your PPS43 build goes well.