It’s worth the investment if you actually plan on gaming. What kind of setup are you running right now? Just a heads-up: your CPU is going to be a major bottleneck for any modern graphics cards, though you can always swap out the whole platform (CPU, motherboard, and RAM) down the road.
Unfortunately, that GPU isn't even close to being worth that much money. You're better off picking up a used card for around $350—$133though keep in mind those pull more power, so you won't be able to rely on some generic, off-brand power supply.
Do you need a case? For that price point, you could actually get a decent, reliable power supply instead.
GPU (if you insist on buying new) -
http://www.nabava.net/search.php?tp=0&q=R7+250xPower Supply - http://www.nabava.net/search.php?tp=...tron+hexa+400w
Also, I’d strongly suggest doing a quick Google search for reviews on eDigital before you buy anything from them.