You could get this stuff from Home Depot for pretty cheap.
This is a good start and in a nice self contained case (though it has SAE stuff too which you don't need):
Husky Mechanic Tool Set (92-Piece)-H92MTS at The Home Depot
On top of that you might want to add a spark plug socket (or equivalently a 5/8" deep), and I'd add one of these:
Husky Metric Universal Wrench Set (10-Piece)-HSPW10PCMMN at The Home Depot
I have 2 of these (one for the car and one for the garage) and they have taken alot of abuse so far.
I wouldn't worry too much about screwdrivers, just one of each is fine, or get a universal one with some bits of different sizes. I wouldn't carry 3 sizes of each
Personally I'd add one of these as well:
Vaughan RM24 14-Inch Professional Rubber Mallet with Flame-Treated Hickory Handle - Amazon.com
I love mine for knocking off stuck wheels, impacting bolts and nuts by hitting the box end wrench with this thing, etc. I use mine all the time.
Beyond that stuff, then I think you need to be looking at specific maintenance that you might want to do, like if you want to be able to to Diff drain and fill, you need a 24mm socket (not wrench) for the rear and 10-12mm Allens for the front (try these:
Husky 3/8 in. Drive 10 mm Hex Bit Socket-H3DHBS10MM at The Home Depot, and
Duralast/3 pcs. hex bit set (70-065) | Driver Bit | AutoZone.com)
Most stuff can be done with just the sockets, wrenches, 2 screwdrivers, and the hammer (yes the hammer is necessary if you have rust, otherwise you will strip off bolts and break heads).
It would be nice to go with the ratcheting box end wrenches, but if they are going to be your only set, then I'd stick with the regular ones, they fit in tight spaces better and they go up to 19mm (ratcheting from HD only go up to 17mm).
Oh, and one more thing that I think it borderline a necessity...
http://www.homedepot.com/p/Husky-Magnetic-Tray-Set-3-Piece-TSE2790/204284889. Magnetic trays are a lifesaver for keeping track of bolts, washers, and nuts.