If your motherboard supports it, both electrically and in term of having a sufficiently decent VRM section, you can go to an 8 core FX cpu such as an 8320/8350 and if possible, overclock it.
You can up the GPU to something like a 1060/580 (GPU prices are comically high atm sadly). And you can up your RAM to 16GB (again, comically expensive atm).
But, here's why you shouldn't do any of that:
The FX platform sucks. It sucked when it came out 7 years ago and today it sucks so much more. It's a dead end. AMD has scrapped it and moved on to Ryzen, which are actually very good CPUs at a very reasonable price/performance ratio.
If you buy more RAM it'll be DDR3, which is also a dead end as all new systems use DDR4, meaning that when you DID buy a new PC, your expensive 16GB of DDR3 are worthless to you.
Also, prices for GPUs and RAM are super high. The RAM I suspect is due to price fixing and the high GPU prices are due to all the bitcoin miners buying up cards like they were made of crack. Great for GPU makers, bad for you and I.
I suggest that you start putting away as much money as you can every month, and wait several months, and hopefully the mining craze will subside again (it always does) and GPU prices will be reasonable. The next version of ZEN and the new Intel 9000 series processors will be out before years end, and hopefully RAM prices will fall as well.
Or if you have the means you can go out and buy a new machine now, but honestly with GPU and RAM prices where they are I don't think it's a good idea, so I suggest waiting. Prices are honestly nearly double what they should be and that's just wrong.
Once you buy a new machine you can sell off what you currently have (selling as individual parts tends to net more funds in the end) and recoup some of your money spent on a new machine.
