First and foremost, I would keep a very detailed log of everything I have produced at the bench. I do that now, but it took me a few years of learning (making the same mistakes more than once...) to figure it out. These days I can EASILY refer to anything I've made and repeat it if I choose, or avoid it if I now know better.
In tools, I'd have skipped the powder dippers and the other powder measures I used and gone straight to the Lyman 55. I also would have bought TWO .38/.357 die sets, so I wouldn't have put off .357 Magnum for so many years simply because I didn't want to "adjust" my .38 dies.
For the more advanced in tools -- I would have done better research before I bought my chrono. I bought the Chrony Beta Master and the interface is horrific. The chrono does exactly what it is supposed to do and measures every round I shoot through it, and I like the way it packs up and it works well, but the user interface is perhaps the worst
of any electronic device I've ever encountered.
Lastly, I would have bought a tumbler a lot sooner than I did, and I'd be sure to go directly to the Berry's tumbler because it's a terrific tool and better than the Frankford Arsenal I started with.