My advice would be to figure out what you think you would want to use it for, and then figure out what attributes the rifle will need to work best in that role.

My advice is worth exactly what you pay for it. But for an all-purpose AR, something with a 5.56 chamber with a 16" barrel and mid length gas system usually fits the bill. I tend to suggest something with a free float rail and flip up sights vs a fixed front sight post, as it makes switching things down the road easier.

Now, there are lots of options that meet that criteria, so the price you are willing to spend will narrow it down to the best options for you.

Visually things don't look too different as you go up the price range usually, but the materials used and testing they are put through improves. There usually is a sweet spot in the mid tier range where you get quality components, without just paying for a name.