So I think the time has come that I feel I should own an AR. To be honest...I've kinda been opposed to the idea that I NEED one, but it's been on my mind as of late. A friend showed me one he recently built using PSA parts for like 400 bucks all in, and said he's very pleased with it. I know nothing about them, but like the idea of bargain shopping for parts over a period of time to put one together. I believe his qualifies as a pistol with a 13.5" bbl, but I would want a rifle, so 16" plus on the bbl. I'm looking for some advice from seasoned AR owners/builders here on what parts to buy, and what to pass on when building a budget AR. I want economical parts, but not junk parts. I want common stuff that interchanges easily with another brand parts. Not really looking for recommendations on complete rifles at this time. All new to me, so....Perhaps there are specific sales from time to time I should be aware of?