he isn't going to get much gaming for $200, the best he could hope for is a reasonable s754 board from a reputable manufacturer and a sempron. make sure he doesn't even contemplate a celeron or he'll have no hope of gaming
well i used an Asus K8V-MX in my grandfathers s754 build and i quite like it. its a fairly basic board but it gets the job done. of course there won't be any overclocking options on the board. i don't have the time to look around but at the upper end of s754 boards you could get an NF3 LanParty motherboard