You will want an AR15 multi tool, a set of punches, an upper action clamp type block, and a lower receiver block that fits in the magwell. It shouldn't run much more than $100. You may also want to pick up a nylon strap wrench from a hardware store (I got mine from Lowes). They can be helpful in installing/taking off free float tubes. Also good for changing oil in your car/truck. Oddly enough, I got all of my stuff from Bushmaster. They have a set of 4 Starret punches that will do whatever you need, as well as the clamps/blocks, and multi-tools.
http://www.bushmaster.com/products.asp?cat=15
Regards,
-Dan