You'll eventually want a completely new PC. That one is pretty old. You could consider putting a 1050ti graphics card in it, as that is the fastest video card that does not need extra power (from the powersupply). IF you do this, some more graphical games will play, but that video card would be bottlenecked by the CPU.
My advice, would be to save up until you have around $1000 and get a new PC.