Good to have another member in the 'Force. Some superb advice here already. Several vendors, including those who advertise on this site, offer very good tool kits, and for an RV-12, don't run to 2 grand. I chose the RV-12 kit from Cleaveland and am very satisfied with it.
As others have already said, their "Main Squeeze" is much easier to use. Nearly all of the solid rivets used in the RV-12 are size 4 (1/8"). They are physically difficult to set with a standard hand squeezer, especially if you have to do a whole group at a time. Not so with the Main Squeeze. Hit the icon link to their site and search it. IMHO, their dimple dies are also a must have.
I also recommend the practice kit from Van's, but realize that most of the RV-12 construction is quite different due to the predominance of pulled rivets rather than solid driven rivets. Still, you will gain a lot of good experience with the practice kit.
An air drill is nice, but I find myself using a mid-price Craftsman 12v battery drill almost exclusively, for about half what my air drill cost. It has so far been adequate to every task.
My tool kit came with 350 #30 clecos. I have yet to come up short, but hey, how could more be a bad thing?
Since so many of the rivets are not the flush type, a DRDT frame seems a bit extravagant for the relatively few places that must be dimpled. Van's has engineered the -12 kit so that every flush rivet location is reachable with a hand squeezer equipped with the standard 3" yoke. I picked up a used C-frame dimpler, and so far have used it only once. Try to avoid buying tools you don't really need, and then add to your set only as you need to. The pneumatic squeezer and a DRDT dimpler frame together would set you back easily more than a grand. They are wonderful tools that are just about essential for any other RV, but I feel are kind of over the top for the -12.
Spend your money on a good buffer motor, preferably on a pedestal stand. Note that I did not say grinder motor. You need one designed for a buffer, which has the extended spindles and turns at 3300-3400 rpm. Put a light duty 6" Scotchbrite wheel on one side and a medium duty one on the other. You will use this rig A LOT. Also get the same wheels in 1" and 2" diameters. These are for use in a drill press (if you have one) and/or a hand drill.
One item that's not in any tool kit I've seen, but is arguably necessary, is a pneumatic cleco tool. Operating cleco pliers hundreds of times a day is about as certain a way to develop tennis elbow you can find, short of playing tennis all the time. I speak from experience...it hurts. Last time I saw, Avery Tools had cleco guns for a pretty good price, around 90 bucks.
Most important of all, if you haven't joined a local EAA chapter, do that first. Hook up with every builder you can. There are other people in Cincinnati who have built or are building RVs. They have knowledge they'd love to share.
Last word: Most of us have found that this isn't a hobby, nor even a journey. To call it either would be a massive understatement.
Glad you could make it.