My 2 cents and I claim to know very little....
1. Get a US made version and true milspec. True milspec, not just milspec sights etc, and no worries that i would get the one dud chinese version...wasnt worth the risk to me.
2. Shoot it a ton and then slowly add things that you want. Better to spend on ammo and enjoy than to spend a fortune on having the brand that advertises the most.
Just what was recommended to me. I did a lot of looking on here and if you are patient there are some screaming deals that come along. D Defense etc....for even below that but.....
I ended up with a good quality off brand (black forge) and it was in the low $700's all in with tax and shipping.
That leaves me a ton for optics (thinking of the holosun 5 series that are coming out soon to replace the 4s) and that will leave me lots for magpul toys, .50 mags etc. etc. Should be all tricked out for not much over $1000 Canadian pesos. Thats a working mans gun that should hold its value and be fun for decades.... your mission may vary...works for me.