Dillon-specific stuff (pickup tubes, dies, shell holders, extra tool heads, etc.)
Any standard die will work in 550. The problem with standard handgun die sets you do not need the expander die, as this is accomplished by the powder thru expander with each cartridge. So getting Dillon or Redding Pro Series dies is the way to go!
Be smart about what you are doing....the 550 is press to get. Much more versatile then 650!
Case in point....if you load 9mm then to load 40 you just need a different set of locator pins and a 40 cal powder funnel.. Costs about 16 bucks vs a full blown conversion kit. Same with 45acp....the addition of 30 cal funnel....and you can load 308......
Min Shopping List....
Press with 1 conversion.
For Handgun Loading Dillon or Redding Pro Series Dies if you do not have dies already so you are buying die set that you only use two of the three dies. Rifle dies....use what you like.
Scale...get the Dillon Mechanical Scale....best value on the market....you will always want a mechanical scale to back up any digital scale.
Primer Flip tray....Dillon is huge.....but RCBS or Lyman or MTM makes one that is about 5 bucks.
Loading Manual.....Lyman 49th for handguns is a must!
If you have dies already...get a separate crimp die for hand gun rounds.
A tumbler is almost a must...you want clean brass to help spotting defects and clean brass sizes easier....and clean brass helps keep the dies safe. There are liquid methods to clean brass with too....and wiping them down by hand is okay...
Optional...
for each caliber you load get a separate tool head and powder die; no need for separate PM. This allows the dies to stay set up and so all you need is to swap the PM out.
The Strong Mount is optional....you can always get it later...make sure your bench is ROCK SOLID. Extra pick up tubes are good idea. The Roller handle is nice, too.