Depends on what you do with your system. It's always better to have a separate video card for moderate to serious gaming. You can get a decent card for under $100.
You mean that is has already built in VGA on the motherboard. The athlon cpu does not have inbuilt Vga as the other CPUs for FM1 motherboards (A4/6/8). So if you use the athlon cpu it uses the motherboard GPU. If you put A4/6/8 CPU then the CPU inbuilt gpu is used?