- Press (single stage or progressive)
- Reloading dies (sizing, depriming if separate, bullet seating)
- priming system (handheld, bench, or press)
- powder scale (with check weights)
- powder dispenser
- Caliper
- Reloading manual/handbook digital or hard copy (good idea to have different ones to cross reference charge weights)
- Case cleaning (tumbler, media)
- Bullet puller (kinetic, collet style, etc)
- Case Prep (trimmer, chamfer/debur)
- Miscellaneous necessary (case lube, trays, shell holders for calibers your loading, swaging tool - only necessary for crimped primer pockets, etc)
- Miscellaneous not necessary but very nice to have (Comparators, case gauges, case annealer, etc)
- Components (bullets, powder, primers, brass)
- A good sturdy/stable reloading bench
The single stage kits (such as the Lee Breech Lock Challenger Kit, RCBS Rock Chucker Supreme press kit, Hornady Lock-N-Load Classic Single Stage Press Reloading Kit, several others) will come with most of what you need.
Quality dies (Forster, RCBS, Redding, Whidden - people have their brand favorites, mine happens to be Forster), reliable calipers for measuring, an accurate scale (if your scale doesn't include check weights, get some quality ones), and quality components and loading with care will produce good ammo. Garbage in = garbage out.
The more money you spend, the more convenience upgrades you get such as faster, accurate, and repeatable powder dispensing, quicker die or caliber changes, easy adjust dies (such as micrometer seating dies), progressive loading, machine case prepping like machine trimming/deburring.