Why is my PC getting bad fps?

"Use 3tb seagate expansion for my games, if I had them on a hdd will it improve graphical quality or will it just cut load times? "

You are limited by the speed at which data can move across the USB bus...that's probably why you are getting bad frames or at least another factor. I would never use an external drive when dealing with large data, because the USB bus is too slow, and also might already be saturated with keyboard and mouse inputs, and pretty much maxed out if you use a USB audio device. I would try moving the games onto the main disk and see if there is any improvement in framerates...most likely there will be a difference.

Nothing is wrong with AMD in general, but that processor is pretty weak for gaming. I don't know what GPU you have because all you listed is that it's a R9. Depending on the GPU, your CPU could very well be the problem, along with if it's a CPU intensive game or very graphical game. You do need to upgrade your PSU, as insufficient power hinders performance of parts, which is another possible reason.