I would get the 2120 instead of the 2100.
The Asrock motherboard is ok.
The ram I would change to CT2KIT51264BA1339 instead.
The video card is going to be the make or break thing, though, and even if you are on a really low budget I would highly suggest trying to find a little bit more money to spend on it.
A 7750 would play games very much better than that card will. Like 50% more FPS. It would make a huge difference if you can find the money to spare for that in addition to the money for the other things. You won't regret it if you can dig it up from somewhere.
what is your budget for this upgrade?
My assumption is $50 or so above the cost of the parts he chose himself as a maximum.