OP. assuming you plan to start reloading for a bolt action rifle, 4831 has it spot on.
As you have surely learned from your reading, a fired case comes out of the chamber very slightly expanded. In a 2 die standard set, the re-sizing die forces the case back to somewhere close to original dimensions. In the process, the de-capping pin normally found in a standard re-sizing die pops the spent primer out of the case. As you withdraw the case from the re-sizing die, you drag the case neck over a button that re-sizes the inside of the neck to a diameter normally appropriate to properly accept, and hold with some tension, a jacketed bullet.
You prime and charge the cartridge separately, using any tool that floats your boat that you and your banker can agree on - simple hand held or other manual priming tools work just fine, and a powder measure takes most of the tedium out of re-loading, although you will still need a good scale to set up and to periodically check your measure - and then the second die - the seating die - will force your new bullet into the re-sized, primed charged case.
It really is no more complicated than that. Two dies, a case holder, something with which to prime and charge, and bob's your uncle. You can mess about with backing the sizing die off to neck size only- what most folks did exclusively unless they were bench rest shooters - and you can mess with the seating die to crimp those jacketed bullets with a proper cannelure, if you really want to. For bullets without a cannelure, no roll crimping with a seating die is allowed, but that's OK, because 99% of your loads don't need a crimp anyway.
Some on here will insist on a neck sizing die, and in some rifles, for some applications, you may wring more case life, and/or more accuracy out of your loads. As long as you know you will eventually have to full length re-size your cases or they won't chamber anymore - they grow with each firing - and they may balk at being chambered as the trophy of a life-time is ducking his head so you can chamber a round, but hey, that's how we learn.
As for crimping, if you insist on shooting big boomers and putting the same un-fired cartridge in the bottom of the magazine, shoot after shoot, or if you treat loaded ammo like a bag of rocks, you may benefit from a crimping die that does not use a roll crimp, so that you can crimp a bullet lacking the appropriate cannelure. It is even possible that certain bullet/powder/seating depth combinations may shoot more accurately in your rifle with a crimp. It is more likely that such a crimp will add sufficient variation to the "pull" that it decreases accuracy, and again, in 99% of cases it is simply an u-necessary step.
2 dies, a shell holder, priming tool, scale and measure, and go for it. Oh, and if you don't lube your bottle-neck cases before you re-size them, a stuck case remover tool!!!