Most games today require a relatively powerful CPU to accompany a GPU, such as an i5 and GTX 970 combo. Arma 3 requires a powerful CPU to run at maximum settings, or even run decently at all, and a mid to high range graphics card to run the graphics. Battlefield 4/1 requires a balance between the two, such as an i5 and a GTX 970 at the minimum (Though I can run it just fine with an i3 and GTX 970 at Ultra preset). RAM is also another factor to keep in mind of, most games today require a minimum of 8gb of RAM.
You currently have an APU, aka your CPU is providing the graphics, so it puts more pressure on the CPU so it can't run at its full potential. If you are going to upgrade your system, find out which motherboard you have and if it supports any new CPUs (In your case, you are limited to AMD CPUs). Ensure your power supply can keep up with any new additions to your system too. I would recommend the GTX 970 to you if you can manage to afford it, personally the EVGA series. I haven't noticed TOO much of a difference with only 3.5gb of vram.
I ain't no expert on these things, so I may be wrong on some parts, but I hope this helps you out somehow. Someone can correct me if I said somethin' wrong.