I am partial to Palmetto State Armory since I live in SC. PSA opened a new store here in Greenville recently which makes it convenient for me although some of their good deals are online sales which are not available in store. Some folks have not given them high marks for delivery time or for communications. My experience with items I have ordered online from PSA have been fine.
I am a relative AR newbie myself. It was hard for me to know what I wanted and there seemed to be endless options and configurations. For my first AR I decided to keep it fairly simple and try for an all around gun, if there is such a thing.
I built my first rifle. PSA had opened a new location in Columbia and I stopped by to check it out while I was in town for work. Saw a sign that they had stripped lower receivers on sale for $49.95 and figured I could not go wrong at that price, so I bought one and put it in the safe. I still had little idea of what I wanted although I was fortunate to have a couple of friends with a little experience with ARs who could help me. Over several months I purchased the parts to build a "complete lower", mostly as I found things on sale. I bought everything from PSA except for my rear sight and charging handle that I bought at a show. I assembled the lower myself which was pretty easy. I didn't try to build the upper from parts since that requires tools and expertise that I don't have. I purchased a "complete upper" in last year's Black Friday sale. It is a pretty basic rifle except that I did purchase an upgraded trigger.
PSA had lowers on sale again for $50 for Black Friday this year so I bought another and am building my second rifle. I think I will make this one lightweight and compact. I chose "flat dark earth" color for the "furniture" where my first rifle is basic black.
I am no expert but my thought process went this way. First, select the chamfering; we both went with 5.56. Second, do you want the "direct impingement" operation or a piston system (the Ruger is an example of the latter); I went with DI. Next, choose the "gas system" which determines the length of the barrel and handguard. Going down in length your choices are rifle length, midlength and carbine. I wanted a 16" bbl and chose a "middy".
Even with all those decisions made there are many possible configurations. Do you want a free floating handguard or the traditional setup with the "A2 type" front sight and two piece handguards? I went with the latter on my first build but may go with one of the slim rails on my second build. The type of barrel is another choice, even with the traditional configuration.
Do you want to use iron sights only? A receiver with the "carry handle" may appeal to you. Planning to mount a scope or other optical sight? A flattop receiver might be a better choice, or you can get one with a removable carry handle.
You can read about other options such as forged v. billet construction. The many different styles and finishes for the bolt carrier group. Twist rate of the barrel. For my purposes I didn't stress over these items. Once I have put a few thousand rounds downrange I may develop the ability to tell the difference.
I have enjoyed learning a little bit about the AR. I hope you will too.