I started building AR15s in 2009 and for the most part they run just fine with standard parts. As I got more into fine tuning and custom builds I find that adjustable gas blocks can save time and money. I prefer ones that can be fine tuned (more than 3 or 4 settings) and can be set with the hand guard on. By setting them properly you will end up with a softer shooting platform that is still reliable. I start by closing it up almost all of the way. With only one bullet in the rifle shoot it and see if the bolt locks back. Once you get the bolt to lock back open it up one or two more adjustments - don't forget to recheck it when the rifle is cold. There are many out there to choose from now so be sure to do your research to ensure fitment and quality.
“If a man does his best, what else is there?”
– General George Patton Jr