You video card is the one item you really do not want to be slow. Because if you have a very slow video card, some games can be jerky, stutter, and just become unplayable. Especially games that are trying to be "photo-realistic". It takes a lot of power to draw those realistic looking frames, and it needs to produce enough frames per second to make your eyes see a smooth game. That is almost always 45 frames minimum, but many people prefer 60 frames per second (FPS).
I would like you to take a look at a performance chart that is updated daily. I am going to link the R7 250 that is in your parts list, and then I am going to link the R7 260, one step up from the 250, just so you can see the difference between these two video cards.
R7...