To the the OP you might consider loading a pistol caliber as a starting point. Straight wall cartridges like 38 special, 45acp, 9mm operate at much lower pressures than a rifle cartridge but still make you go through all the proper reloading steps. You are going to have to learn how to read and understand the recipes in the books, about powder and projectiles, seating depths, what over pressure looks like, and dozens of other things. If you make a mistake on a pistol caliber it is usually not quite as destructive or as life threatening.