“Low budget” is a hard term to define in the world of rifles. I am fully aware that a month ago I could have purchased a complete Anderson upper and complete lower for $320. In that same time frame I assembled (actually my daughter did) a $710 “budget” rifle. More than a few guys I know and plenty I don’t know would tell you a $900 Colt is what they consider budget class and I think all of us are correct.
After a few builds under my belt I much prefer an “oops” kit with individual controls from the likes of Phase 5, Battle Arms, and Strike Industries. They look, feel, and function great for not much more than a full LPK.
If I’m spending upwards of $300-$400 on a rifle it may as well be accurate which means buying a better barrel than some $45 iffy and splurging for Melonite for barrel, gas tube, and bolt. Beyond offering a longer service life the benefit of less cleaning and care plus corrosion resistance makes it money well spent.
Again perception of the term “budget” is key. Despite splurging on dinners out, flowers, and gifts, my wife was far cheaper when we were just dating. Likewise building the rifle you want now will cost less than replacing the one you never wanted.