I wouldn't pick any of those boxes, myself. I see a bunch of stuff in all of those boxes that I wouldn't fish. Where you plan to fish will determine what flies you should plan to fish. Lentic or lotic water? High mountain lakes or valley reservoirs? Freestone streams or tailwaters? If you are fishing some place new, I would stop in a fly shop and talk to somebody. Get the lowdown on what's hatching while you'll be there, then buy flies.
Some of the things that can work across most locations are general nymphs (hares ears, prince nymphs, rainbow warriors, sow bugs, BWOs, caddis, damsel/dragonfly nymphs (especially for stillwater)) and types of streamers (wooly buggers, leeches, sculpin patterns). Dry flies can be really hit and miss, but some search patterns like hoppers and PMXs are good flies to always have.
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C is a more well-rounded box but that price is ridiculous for what you get. You're going to want a good mix of dry files, nymphs, wet flies, and streamers. That's what you get with box C, but you should be able to get those files for the price of box B.
That price is actually pretty good. I would pay $1 per fly for any one of those flies.