Unless you want to build something other than an M4gery right now buying a complete gun would probably be cheaper. Describe want you want and folks will better be able to help you.
Del-Ton was a great deal and went together fine for me. However, if you want an M4gery, as stated, it is cheaper to buy. If you already have a stripped lower, their kit is $465 + any upgrades and shipping.
you can also check out brownells website and play around with their free online AR building software to narrow down what you may or may not like on yours. i use it but ignore their pricing as it is high and stuff can be found cheaper elsewhere
Do what I did, wait for 1500 and price shop for what you like.
It may take all day, but you will be below your price limit.
I built mine for under $500.
model1sales.com does have good uppers i usually get them at the indy 1500 gun and knife show they come to every one. the next one is August 27,28 and 29 Welcome to the Indy 1500 Gun & Knife Show