To get started with the most basic/starter reloading set up, you will need this:
1. Press (single stage) O frame
2. Scale (beam scale) for weighing powder charges and bullets.
3. Priming tool (some presses come with a priming tool, LEE for example)
4. reloading die set for your chosen cartridge AND shell holder (LEE dies come with shell holder)
5. trimmer (not needed for most handgun cartridges) use the LEE handheld trimmers for about $15
6. powder funnel
7. loading block (easy to make it yourself with a piece of 2x4 and a drill)
8. case preparation tools (inside/outside neck chamfer, large and small primer pocket cleaners)
9. caliper (digital or dial)
10. bullet puller, because you will need one eventually
11. reloading data - online and manuals (Lyman is good)
This is a basic setup that will make quality ammunition and is all that many shooters will ever need. At some point you may want to add a powder measure and some kind of brass cleaning machine but you don't need it right away. An experienced reloader can make 50-100 cartridges per hour with that setup.
Reloading isn't terribly complicated, it just seems like it when you 're starting. Read manuals and watch videos, but you won't really understand it completely until you do it yourself. Get a press, a die set, and brass, then deprime it, trim and chamfer, seat a bullet. Practice setting the dies with dummy rounds before you start reloading live cartridges.
The Lyman Reloading manual is very good. Gun Digest made some online videos that are worth seeing:
episode-01-basics-reloading
episode-2-tools
episode-3-case-resizing
episode-4-primers
episode 5 Powders
episode-6-bullets
episode 7 specialty brass
episode-8-troubleshooting
episode 9 Primer Assembly
episode 10 cartridge assembly
hHickok45 Reloading Basics