Let me just help you out by mentioning that there are nearly 1000 sites that sell parts for builds.
You just haven't looked hard enough yet. You haven't even tried, have you?
Many suppliers sell complete kits: All the parts minus the lower receiver. The receiver requires an FFL licensed dealer to transfer it, but the kit-minus-receiver doesn't. Buy yourself the receiver first. Then shop around for the kit in the configuration you want.
Kits are generally about 20% less than buying individual parts.
Get a book on building the AR, or go to a web site like ar15.com where they have a sticky on it. It's really easy.
I built my first 5 rifles back in the mid 1990's with only one tool (the carbine stock wrench). I didn't buy any specialty tools until later. If someone tells you that you have to buy lots of special tools, the answer is No.
Take a tiptoe through Gunbroker just for fun. Go to Firearms Parts. Then click on AR and you'll get 50 pages of parts for the AR15. Also go to manufacturers sites like DPMS, Rock River, Olympic, CMMG, and all the rest.
You just haven't tried hard enough yet.