If he wants to get into 40k, Orks are a solid starter army. With as many boyz as you get, you can make plenty of mistakes and not be massacred like other armies.
I'd advise to wait and save up cash for the new Ork releases sometime at the end of this year. With new trukks and new bikes, it'd be a waste to buy the box they have now and have most of it be outdated within a few months. If he really wants to start getting into it now, a box of boyz is never a bad investment, you'll always need more.