First off I need to explain one thing, NO "FM" based motherboard (FM1, FM2, FM2+ or AM1 (FS1b) comes with "integrated graphics cards". All of these boards have to have a APU (with a built in GPU) or a Discrete Graphics Card (installed in the PCI-e slot) in order to render video signals.
Dual graphics is a technology which allows a APU (with a built in GPU) to "share" graphics rendering with a single Discrete Graphics Card. The compatible Discrete Graphics Card which can be used depends on the APU which you are using. You can find the recommended Dual Graphics charts on the following page.
From what I know about Dual Graphics the A4 6300 does not have a recommended Dual Graphics card. Some people have been able to get some Discrete Graphics Cards working in Dual Graphics mode with this APU but it seems that there is no "stable" Discrete Graphics Card which will always function with it.
Personally, due to the low end specifications of the built in GPU (in the A4 6300) I would recommend just buying any Discrete Graphics Card and using it in Single Graphics mode. Even a R7 240 has around 30% more performance by itself then if you were to get the A4 6300 working in Dual Graphics Mode.
128 Stream Processors
760 MHz GPU Clock
Memory Type - DDR3
320 Stream Processors
780 MHz GPU Clock
Memory Type DDR3 or GDDR5 (remember that GDDR5 works about 2x as fast as DDR3)
As you can see from the above specs the R7 240 has almost 3 times the number of Stream Processors and as such would way out preform the A4 6300 when used in Dual Graphics.
Remember that Dual Graphics can at best double the number of Stream Processors which are being used for graphics rendering. Thus the A4 6300 would be able to use, at best, around 256 Stream Processors when in Dual Graphics mode. Also Dual Graphics will only be enabled when playing a CrossFire compatible game in "Full Screen Mode". As such any other program would not benefit from the extra performance which Dual Graphics would provide.
So again, just buy any R7 or higher Discrete Graphics Card and use it by itself.