I remember my first build, I sat aside a whole day and was like "I'm finally gonna build my first AR" about an hour later I was like "that's it."
I recommend just using a box cutter blade to hold in the take down pin detent while you install the pin. You will need punches, castle nut wrench and a center punch to stake the castle nut. Also I use a piece of bamboo skewer as a slave pin to hold the trigger group in while I push the real pin through.
I put my first one together at 14. Built my first upper at 16. Watched one video on putting together a lower and figured it out pretty easy. We had a snow day so I got to stay home from school that day because of the weather. I remember putting my lower together at the kitchen table pretty quickly and slapping the upper on and stepping outside and firing 30 rounds of Silver Bear .223.
When I was buying my upper for that lower I built I was researching them and kept seeing a lot of 14.5” barrel uppers so I got to seeing what the benefit was. I had no clue 16” was the legal barrel length at my young age haha. Glad I researched before buying or I would have had a SBR and didn’t even know it.
Went into the local gun shop with my mom with a print out of the stripped lower I wanted off of Palmetto State Armory. It was a “Gadsden” lower. Had the dont tread on me flag on the right side of the mag well.. that was the first time that that gun shop ever ordered a stripped lower, they didn’t know AR building was even a thing. That was about 12 years ago now…
First build I did was that PSA Gadsden Lower with the M4 style LPK and then I ordered a Del Ton Pencil Barrel carbine upper for it. I think I remember putting a small scratch in the lower trying to put the pin in for the bolt catch, somewhere in that area.. Years later it ended up for sale on OSA and don’t remember who got it so if any of y’all have that AR I may be interested in buying it back from you.