Are you going to buy the upper pre-assembled? If not you'll need a torque wrench and barrel nut to properly torque down the barrel nut. There are people here that do it by feel but I'm a buy the Army manual guy.

If you don't buy the upper pre-gauged against the bolt you should buy a go-no-go gauge set. It's simpler just to buy the whole upper already assembled and have them head space test the bolt for you. There are people here that will claim that it's a waste of time but again, by the book, it has to be done.

Assembling a lower is nothing. You'll need a pin-punch set and a small tack hammer or the like.

If you're putting a collapseable stock on you'll need a special $6 pin wrench if you don't have one already.

A common hex driver is needed for the pistol grip.

The hardest part of the eight rifles I built was that darn front pivot pin retaining pin and spring. First buy extra pins and springs! They're like a buck for the pair, if you lose one it will take a week to get there. Second wear eye glasses as that spring will push the detent hard enough to put it into your eye! I bought a special tool from Bushmaster to help but it didn't. I use a wide flat knife blade to compress the detent on top of the spring while sliding the pivot pin into the holes.

I've never used a receiver block as I have a pretty nice gun vice used for cleaning that works well enough. My wife lends an extra set of hands when I need them.

Have at it!