First, RCBS reloading equipment is far from junk. Second for 223/5.56 I think you'll be a lot better off if you start with a manually operated progressive press like
Dillon's 550B. (It can also be used as a single-stage press if you so choose.) Among other things you'll, definitely, need a: powder scale, (I recommend a non-electronic/balance beam scale.) dial caliper, a vibratory tumbler, case mouth chamfering/reaming tool, and some sort of case trimmer with the appropriate shell holder, and neck collet. (RCBS makes all of this ancillary equipment.)
Personally, I don't like to reload without final checking my finished rounds with an appropriate caliber (Wilson) case gauge; and, in order to more easily set up a progressive press like Dillon's 550B you should have one of Dillon's nice 'n flat lock ring wrenches.
YOU WILL, ALSO, NEED A WOODEN BENCH THAT'S IDEALLY, 'BARSTOOL HEIGHT', (OR SLIGHTLY HIGHER THAN YOUR BELT BUCKLE).
Several die manufacturers offer carbide 5.56 sizing dies either singly, or as part of a complete set. Dillon dies have always worked well for me; but, I was never shy about sending any sizing die I thought had too loose a base back to Dillon in order to get it tightened up. RCBS and Redding sizing dies can be had in, 'small base' configuration - Which makes the cartridges these dies produce ideally suited for use in a semi-automatic/full automatic firearm. Under the heading of, 'Nice To Have' I'd add plastic ammo boxes from someplace like Berry Manufacturing; an RCBS, 'Case Prep' Station; and if you go with a Dillon progressive you'll need a toolhead stand.
If you haven't already got a,
'Speer, #14, Reloading Manual' then get one.
'The ABC's of Reloading' is, also, good to keep on the bench. I used to enjoy reading reloading manuals. The technical front and back sections of the Speer Manual were always worth, 'gold' to me; and I learned a lot from both of these books. If you're not aware, NRA Training, now, teaches reloading. If you like, call Fairfax @ 703-267-1500 and ask the Training Department for the names of Reloading Instructors in your area.
By the way my idea of a perfect reloading setup is to have an RCBS, 'Rockchucker' on one end of the bench, and a Dillon 550B on the other. In between is the manual powder measure (Often shelf-mounted) case/cleaner vibrator, and case trimming lathe. (Mine was stored under the shelf when it wasn't in use; and bolted to the front of the bench with a small C-clamp when I was using it.) Hope this helps you out.