I'm only around 18 months into reloading, but I'll say I dove into it head first. I read and read about the topic but in the end, found no definitive answer for me personally. IN the past year, I've loaded more common components but I've learned a thing or two.
I started with a Dillon 550 for 9mm, 44 mag/spcl, 38 spcl. The machine is fine for all of those but my favorites on it are 44 mag (NOT using a Dillon powder drop), and 38 spcl. For 9mm I'll probably get a 750 one day with the works for real automated loading. For now, the 550 is ok for that round, but not the best. I'd have no interest i loading 38 or 44 on a 750.
I started loading match 223 and for that I bought a single stage...and I think it is perfect for that task, no complaints. I know people load 223 in bulk, but I shoot steel cased and when it's cheap, there's just no reason to ever load it. I'm just about to begin loading 460 S&W and again, I'll definitely use the single stage for that as well.
Dillon dies are superb, but they are 100% "set and forget" as in you set them up for one specific load/projectile and leave it that way. Adjusting them for specific rounds is a serious pain in the rear, they have no fine adjustment options. What they do offer is super easy cleaning...again, for those mass runs of ammo.