Components are where you can find them right now, still... Expect to pay 80-100 per 1000 for primers. Powder is available as long as you arent terribly picky on brand. Bulk bullets are in good supply, some match stuff, not so much.
Check your twist rate to determine max weight you should shoot. Anything over a 9, go with 55s. A 9 will shoot up to a 62 pretty well. An 8 will shoot up to a 77 well. A 7 will shoot up to 85 or so. Obviously every barrel and gun is different, as Ive seen 77 SMKs shoot just fine in a 9 twist. So just general guidelines.
Beyond that? If you are building blaster ammo, a decent ball powder is a good place to start. TAC, H335, Staball Match, etc. If you are pursuing accuracy, look for 8208 XBR, Benchmark, Varget which are extruded powders, which are generally more accurate.
Primers can be bog standard small rifle. Never felt a need to shoot mil primers like 41s in any of my 223 stuff, and Ive run some pretty stout loads.
Cases can pretty much be anything. You can buy tons of once fired stuff on the internet, and thats what I recommend. Dont get too wrapped around the axle about headstamp sorting. If you want matching headstamps, go buy new brass, instead of sorting 2000 cases for headstamp, and having 300 of this, 200 of that, situation. Starline is a good source for new brass thats decent quality.