About to buy my first, don't know much about the AR platform.

I was just going to buy a completed rifle and after some experience with it build a second one if I'm wanting a (significantly) higher quality build or a more customized build.

I'm (probably) buying an Eagle Arms M15 for $540.

Manufacturer Number: 15EA01

Action: Semi Auto

Barrel Length: 16" 1:8" RH Twist

Overall Length: 32.23"-35.5"

Finish: Anodized Matte Black Finish

Grips: A2 Style Grip

Stock: 6-Position Collapsible

Material: Forged 7075-T6 Aluminum Upper and Lower

Sights: Optics Ready Flat-Top w/ Mil-Std 1913 Rail

Am I about to make a mistake? If I could build a better one for around the same price I'm open to that too.