I really recommend the Brownells action rods for assembling uppers, instead of vise blocks around the upper receiver. It's faster and easier, and doesn't stress the receiver like vise blocks do. It's also useful for muzzle devices, and for installing barrel extensions if you make your own barrels. https://www.brownells.com/gunsmith-...el-extension-torque-tools-prod27452.aspx
A tip on using one of these reaction rods - instead of setting it up like the Brownells video shows, just clamp a 1/2" drive breaker bar in the vise with the 1/2" drive pointing up. Then you can just set the reaction rod on that, and the receiver and barrel on top of that; it's really quick and easy that way. You can even use the same method with the breaker bar in a trailer hitch receiver in the field if need be to tighten a muzzle device or something like that.
Also there is a nice 2-piece punch set from Geissele for the little gas block roll pins. https://www.brownells.com/gunsmith-...nches/gas-block-punch-kit-prod68034.aspx
For that matter, I suggest just starting with Brownells for your AR building tools. They have most everything you need, and also have some good videos on assembling ARs.
Some Loctite products are useful tools for assembling ARs too. I recommend two in particular:
- Blue #243, medium strength that is oil tolerant (the more common #242 has similar strength but is not oil tolerant, no advantage to using that one). I use #243 on the buffer tube and castle nut when installing on the lower receiver, on gas blocks (both on the set or clamp screws, and between the block and barrel), and on muzzle device threads.
- Green #680, high strength sleeve retaining compound that cures in up to .015" air gap; this stuff is useful for bedding barrels in loose fitting uppers, and for securing handguards on barrel nuts for belt and suspenders prevention against loosening.
I've been using a fairly cheap DPMS AR15 wrench for barrel nuts and buffer tube castle nuts; I wouldn't call it a high quality wrench but it's done the job for at least 10 years now. There are probably better options to choose from these days.
The last tool that comes to mind is a pivot pin tool set; they aren't completely necessary but do make the job easier. I use something a little different than this one, but this looks like it'll do the same job. https://www.brownells.com/gunsmith-...oll-pin-intallation-tool-prod126521.aspx
Hope that helps!