The APU was designed for people who need enough videocard power for something like HD video streaming, but do NOT need enough videocard power for more demanding tasks, like gaming. These people can use the APU and save money by not having to buy a gaming card.
I realize that you are on a tight budget but there are always people on these forums with APUs and they are unhappy with game performance, and they want to know what card they need. Almost always, no card will help them since the APU itself is the limiting factor.
You want to build an APU based system for $200, then add a videocard that cost around $200 to it. That's not a great idea. You'd be better off buying an older(ie Sandy Bridge) Intel quad core based system and adding...