New to the AR? Need help with your first purchase? READ HERE FIRST!!

[HeruMew]

Want a custom built AR under $1400 as a beginner.

No, you don't.

I mean, if it's your only rifle and you don't plan to use for HD, go for it. Build a light, colorful, range toy.

For 1400, go with these few options, especially as a beginner:
Colt 6920
BCM Midlength
BCM in General.
Hell, even your price range permits some high level factory options of rails and furniture.

Seriously though. Spend 800-900 on a colt, buy an aimpoint/higher end optic, and use the rest of the cash for a class or ammo. Or both. Then, shoot it. A lot.

If I had 1400 laying around for a rifle, I would do that today.

If you want to build a rifle, that's cool, but you won't know what you need out of your rifle for a few thousand rounds out of a basic, out of the box, reliable model.