It is definitely a mountain of information to take in. I built a fairly cheap quad to practice flying and it does take some commitment, but once you (he) figures it out it will be smooth sailing. I think buying him parts is the way to go as well.

Here's some of what I used. There is almost certainly better stuff, but this should work.

PDB--$10

Flight Controller--$27

Controller and RX--$50

Battery--$17 (buy 2 or 3, they only last a few minutes)

Foam Landing Pads--$7 (Not needed but make for slightly softer landings)

I think that's all you need to get started. Not sure if he has soldering equipment, but that will definitely be needed. Again, can't say definitively this is the best or cheapest stuff, but I think it's everything.

EDIT: I left out anything specifically for FPV. If he hasn't flown much or at all it will be a while before he's going to need that stuff anyway.