I hope some AMD users will chime in because I'm not familiar with them. I use Intel because I know more about them. If he decides to go with Intel, he should look for a motherboard that is compatible with the most recent Haswell Intel processors such as a Z87. Things he should look at on a motherboard are how many USB ports there are; how many would he prefer to be USB 3.0 should he get any 3.0 peripherals; what quality of onboard sound does he want if he is not putting in a discrete sound card....
Just as a starting point, this Gigabyte Z87 UD3H is an excellent mid-range board with tons of features. Asus, MSI and ASRock all have good motherboards. He could go up or down in price as his budget allows, but I would definitely suggest getting the best one he can afford. One pitfall to avoid is to get the most expensive one out there if it has all kinds of features you'll never use. Newegg is also a good resource to read actual user reviews. I always throw out the one egg reviews as they are most often from people who complain about things that don't really reflect the quality of the product. Gigabyte Z87 UD3H
Another thing he should consider if he's upgrading an existing computer is something Homer mentioned. If he is using an old case, will it accomodate the larger ATX form factor or will he need to go with a mini-ATX motherboard? Also if he's using an old case, will it have enough fans for cooling if he's building a gaming computer with a discrete video card that will be pouring out a lot of heat? I wouldn't even consider using a small older case for a gaming computer... There are plenty of decent new cases out there for $50.
The eCollegePC website has a great configurator. He might go there and play around with different configurations. Maybe start with one of their gaming series computers and go from there. Even if he doesn't buy from them, it's a good place to see what different builds might cost.