As you can see above, there's many different thoughts on how to get into ARs, so I'll throw in my $.02
First, if your budget is $1500.00, I would first start by going through the stickied picture thread at the top of this forum, to see what sort of set-up appeals to you. Quad rail?
Pistol grip type?
BUISs? A carry handle?
M16 rifle or M4 carbine?
There are so damn many different configurations, you'll need to figure out what you want.
I myself would probably blow your entire budget on the base AR, getting something from Daniel Defense or BCM with a quad-rail and VFG (I like the DDM4-V4 myself)....plus some mags and ammo. Then over time I'd look at an Eotech or Aimpoint optic, or perhaps something magnified. Be aware, optics can be very, very expensive.
I love Mustangs.....a lot.