I would advise to buy what you can afford and modify it over time as you make preferences. I've built about 20 ARs over the last 10 years and I've had $2k Wilson Combats, $1.5k POF (piston driven), $500 Del Tons, DPMS, Bushy, Spikes, etc. I've played with the new Rugers but haven't owned one. For the most part, with the exception of proprietary piston rifles, they are mostly the same. There is only a hand full of forging companies that forge the upper and lower receivers for most major manufacturers. And exception would be the billet pieces but they are a lot more expensive and pointless unless you want to give it a torture test by running over it with a tank. A company called Tool Craft in Marion, NC makes bolts and bolt carriers for most all manufacturers including Freedom Group who owns Remington, Bushmaster, DPMS, Advanced Armament, and Para Ordnance.
What makes the biggest difference is cold hammer forged barrels. FN and Daniel Defense make such barrels and they are awesome, but more expensive. The best trigger for the money is an ALG Combat kit and replace the springs with JP Enterprises light weight spring kit. It makes a clean, crisp break at 3.9 pounds in my rifle and it only cost me $75. Most AR aficionados swear by Geissele Triggers that cost around $225, well the "G" in ALG is for Geissele because Bill Geissele's wife owns ALG and that is her initials.
I am a believer in Nickel Boron coated bolt carriers and bolts. It makes clean up so much easier. Piston rifles still get dirty too, its just not in the bolt and my experience is that they aren't as accurate as DI rifles.
My current setup is a Bushy (I got it on a trade) with a flat top upper,16" H-bar barrel 1/8 twist, ALG trigger with JP springs, Guntec 15" keymod rail, and a magpul stock and grip. I can shoot a 3 inch group at 100yds with no optics just flip up sights .