You can never have too many tools
When I first read how many tools Jim Cone had, I thought he had gone overboard. Now that I am building my 12 I totally agree. I have 2 rivet squeezers, and wish I had 3. The Avery squeezer is very sturdy, and I have it set up for rivets. I also have the stainless steel one, which I use for dimpling. I agree with Marty that a second micro-stop CS tool would be helpful. A guy a couple of hanger over loaned me a bunch of the side clamp clecos, and it is worh having them. He also gave me an air cleco tool, it is very helpful for the wings.
As far as parts, I wouldn't order any just yet. I did order extra rivets, and wish I had held off. Van's gives you enough. You will probably have to order a replacement part or two and can get anything you need then The slowest and most tedious part of the project is smoothing and deburring. I could not live w/o my scotchbrite wheels. Get a 6" and at least 3 of the 1" I also got 6 3" wheels on EBAY for $10, and use them a lot.