Make sure you balance your spending across all the factors, and for your skill level and intended purpose.
Other than the rifle barrel and muzzle crown, I think one of the biggest factors is the bullet itself. I've seen some low quality bullets that just would not shoot less than 2" at 100 yds (pulled military surplus). In the same .223 rifle I was able to get Nosler 69 gr HP to shoot 1/4" - 7/8" groups.
The next significant factor is powder and charge weight. I have tested a variety of .223 bullets and four powders and some combinations everything seems to shoot well (68-69 gr BTHP and any powder) and other bullets the most accurate powder can still vary from 2.5" groups to 3/4" groups.
Along with decent quality bullets and working up good powder charge ladder tests for them, you need basic case prep. I use regular full length size dies, measure and trim cases, uniform the primer pockets and clean the case really well. That is about it and in different off the rack rifles I can usually find several sub-MOA load combinations. At that point I think I become the limiting factor so I don't put more money or effort into tuning my handloads. Consistently getting 3/4" - 7/8" groups, and occasionally get a 1/4" or 1/2" group is plenty good for my purposes.
To get any tighter groups I am not sure if a better barrel, better dies, better cases, or more sophisticated case prep would be more beneficial.
You might get 100 or so of the Norma or Lapua cases to use for working up test loads. Then have a couple hundred or mre of cheaper cases such as Winchester and see how your loads perform in the Winchester versus your Lapua tests.
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