Welcome Alex. While I have some thoughts on which tools I found essential and which less so, I am on my first build so more experienced hands here will likely have better advice (see my disclaimer ). So, disclaimer out of the way...

For the frets, the things I found most useful were the 12" radius sanding block and the crowning file. I bought a notched straight edge, and it was useful but I know that others have techniques for getting the neck straight without one. I would research that as an option since it's one of the more expensive tools that you will pretty much only use once per build. I also bought a fret rocker but could have lived without that as well. In a pinch you could always make something similar by buying a cheap metal straight edge at a hardware store and cutting it into pieces with a hacksaw. You just need several lengths that can cover a span of 3 frets at different parts of the fretboard. Or just go without.