Online Community of Zenith Builders and Flyers
Can't directly comment on the Zenith tool kits as I didn't buy one. What I did was to take their list of tools and go shopping at Yardstore.com. I think I save a bit of money that I no doubt blew through somewhere else.
If you have an reasonable cordless drill, I think you could skip the air drill. I say that, but ended up finding a used right angle air drill that I am starting to love. It sure seems to make for cleaner holes than my Makita. Could be the bits.
The only problem with sourcing your own tools is that with the Zenith kit you get properly domed riveter heads. Not a big problem as you can do it yourself with a dremel. Somebody here has a great youtube video describing how.
It was a quick way to get started with the tools, but I think you could do it cheaper. Just buying the riveter would make it easier. I used 3 very cheap Harbor Freight air drills and my cordless drill instead of buying the air drill. With the three Harbor Freight air drills I rarely changed drill bits. Just my approach.
You'll need at least one of the riveters from Zenith, they come with the machined heads that make the outer dome shape on the blind rivets. I bought the air riveter from Zenith, then found a hand riveter with the same heads on ebay, sold by a previous builder. Also, I love my Sioux air drill, works great, and found it on ebay for about a third the price of new, the things are indestructible, spin at a higher rpm than any battery operated one, lighter, faster, etc.
Of course you'll then need a $500 compressor for the drill and riveter, but...
As far as Clecos, you won't absolutely NEED more than they recommend, but you'll WANT more to make your life easier.
You'll also need other random stuff that is not in the kit for drilling, deburring, clamping, etc that you'll discover along the way
Bottom line, get the riveter, buy your other tools as you need them.