My experience is as follows. My first one was a build. I didn’t buy the cheapest parts that I could find, but I did try to save where I could. Having the AR turned me into a “gun guy”. Being a little anal, I wanted a factory rifle, not a build with mismatched upper/lower and parts. So, I spent about $1200 at the time on a
LMT, which made me feel better about the reliability factor, but in actuality, probably wasn’t any more reliable than the build. After awhile, I decided that b/c I shoot leftie, I wanted a KAC because they make an ambidextrous lower. The KAC is the cat’s 17’in meow.
If you have the money, go ahead and buy a top tier AR. It will be expensive but you will buy once/cry once and have peace of mind. Also, the more expensive guns were available when the parts and cheaper guns were/are nowhere to be found.
Don’t forget, you will need more than 20 rounds and 2 magazines. An optic isn’t a must but makes things a lot better.
ETA: there are certain tools that you will need to do it right. You can skimp and get it done but it won’t be easy without them. Save yourself the aggravation and skip the building.