Build or Buy?

[WillD]

I'm expecting the last of my parts to arrive any day so I can begin my first AR build. I was rather surprised to see so much discouragement to Traxx's question. I don't consider myself "all thumbs" and I'm not deterred because of the wealth of information available. That said, in order of importance, what do you all consider the most important items in an AR build; assembler, barrel, trigger, upper/lower receiver manufacturer?

Thanks, Will