I agree with the additional needed items listed above and would like to add a chrono into the "extremely useful to have" list. I would however, like to offer a differing opinion on absolutely having to start with a single stage press for safety's sake. If start up cost is the primary limiting factor, then I do agree that a single stage may best be suited. Good ammo can be produced for tremendous savings by reloading and a single stage is without a doubt cheaper than a progressive.
However, although I initially spent a greater amount on my Dillon 550 and all the other necessary equipment, it quickly paid for itself. As far as the safety aspect, I started reloading on the press one case at a time, essentially using the press as a turret type press. I could have easily batch loaded, using the press almost like a single stage, but handling so many cases, so many times just seemed cumbersome. When I became more comfortable with the reloading process, I progressed to using the press as was intended, as a progessive press. With a good progressive press, I am biased to the Dillon as that is all I know, one can always start slow and then go progessive with the same press when you're ready. A single stage is always going to be a single stage. I do not load for rifle, (way too much case prep for my tastes), so I don't know if the single stage is mechanically more suited to producing more accurate ammo than a progessive with its moving shell plate.
I shoot at least 200 pistol rounds a week, usually more if my wife and I can make it to a match. To be honest, I am not one who really enjoys reloading, I reload so that my wife and I can shoot for an affordable cost. I am extremely careful every time I am reloading and pay very close attention to what I am doing however it seems this would be necessary whether using a progressive or single stage.
As far as a progessive being more complex to operate, I really like the fact that I can reload for multiple calibers and not have to readjust dies. I just swap out tool head, the shell plate and if switching to .45 ACP, the primer slide bar and tube. Seems simpler than having to change and adjust dies every time I change from belling to seating to crimping even in the same caliber. I'm not knocking anything that's already been posted, just trying to offer a different view on starting with a progessive.