If you live in the UK Maplin sell a reasonably price, £50, starter set for the rpi2 which comes with a keyboard, mouse, wifi dongle and usb hub along with a noobs sd card. A lot of online retailers have a Raspi starter set, including Rapid online, adafruit, sparkfun, all of whom give you a reasonable price and as long as you go for a reputable retailer you won't have any trouble - i.e stay away from cheap eBay lots.
Main things to look for in a starter set is a keyboard, mouse and an SD card of at least 8Gb. If he is interested in the electronics side, look for ones which come with a large breadboard along with the ribbon cable and breadboard adapter, some will even come with basic components.
I agree with C-3P0, I would recommend the official Raspberry pi user guide from the raspi foundation, as well as Simon monks book ( cant remember the title), and there is another called Raspberry pi projects, I cant remember the author. If he isn't a fan off books, there are a million tutorials online.
