I would suggest focusing on a single program -- based on what you have described, he will quickly gain elite status that way, for additional benefits.

You didn't say where he is located. Look at the flight options available from his nearest airport to the destinations where he will be traveling (Dubai, Ridyah etc) and narrow down the list of airlines to those that offer either direct flights or good connections. For each of those airlines, identify the alliance (Star Alliance, OneWorld or SkyTeam) -- and note that some airlines, like Emirates, do not belong to any alliances.

You may now see that most of his travel could be concentrated on one alliance or another. If that's the case, I would suggest picking one airline in that alliance; he will gain credit (both in miles accumulated and elite status gained) to that airline's program for all flights in that alliance.