My best .204 groups are with 39gr Sierra BlitzKing bullets, 26.3gr of Winchester 748 powder and CCI Magnum Small Rifle primers...The brand of brass seems to be of little matter, just trimmed and processed to spec in most manuals..This combination works best in both my AR and my CZ..
As far a reloading starter kits,,,Someone else will have to comment on those two...I've had the RCBS many years ago and it was nice for the purposes I needed, but things may have changed over the years..