Before getting lost in all the bells and whistles that are ARs, find what its purpose will be first.
I dip a little into this in another blog - https://www.mymilitia.com/blogs/entry/36-mission-purpose-asking-questions/
brands for complete buys and builds - https://www.youtube.com/watch?v=mX85uQHrLNo&t=1s
rifle set up - https://www.youtube.com/watch?v=84KBHdpKB1c&t=7s
most important rifle upgrade - https://www.youtube.com/watch?v=lCyVLULUaxI&t=620s
mlok is better than keymod - https://soldiersystems.net/2017/05/05/details-on-the-ussocom-sponsored-keymod-vs-m-lok-test-conducted-at-nswc-crane/
flash hider test (there’s also a part 2) - https://www.thetruthaboutguns.com/ar-15-flash-hider-shootout/
barrels (be sure to watch all 3 parts) - https://www.youtube.com/watch?v=e2X1iaQbjg8&t=15s
If you want a more interactive forum with dudes that won’t suggest crap items, join the FB group “Regular Guy Training YouTube fan page”. From there read the rules and it will tell you many of the brands to stay away from for guns you’re betting your life on.
I would also advise taking advantage of the “poll” option when asking if something is good or not. Its easier than scrolling through comments.
What pistol - https://www.youtube.com/watch?v=O1B7BYtO3_U
stay away from 40 cal -
glock melt down - https://www.youtube.com/watch?v=ub4OswUhLwo
Advise for pistols: keep internals stock, get good sites, get a light, stick with factory mags, get a good gun belt (I recommend blue alpha belts).
When choosing a pistol (and light) look at the price and capacity of its magazines, look to see if the makers of the accessories your wanting make it for that model, find which parts break often (its a machine, something always breaks) and keep a couple on hand, get a good holster.
That about wraps it up for this one. Let me know in the comments if there's something on this subject you would like to know more on.