You don't need anything special except for a vice, an upper receiver vice block, a hammer, a cheap set of punches and a torque wrench. A barrel wrench is recommended for installing the barrel nut (in conjunction with a torque wrench). You can buy a torque wrench, use it once and return it if you are trying to save money. I bought one for about $40 at a local auto parts store and kept it for future use. Some don't even use a torque wrench and get along just fine. I prefer to use one so I know it's done right.
Some jig their upper receivers in a vice using pieces of 2x4 and get away without using a vice block.
Shown here
You don't need a barrel vice block to install a crush washer & flash hider if you use 2 pieces of 2x4 to pinch the barrel in a vice.
Shown on this page. In my experience you do not even need to pad the 2x4, but you could use some cotton t-shirt or something if you want to.
I use lythium grease for the barrel extension and barrel nut threads.
You don't need a roll pin punch set or starter set. Just a cheap set of punches work fine. I bought a set of punches at a local Harbor Freight store. Special punch sets would be more convenient if you are building many ARs.
You don't need a breaker bar.