Krazy is right, you have your tubing on your pump the opposite around. The connection at the front SUCKS in to the pump and the one on the top PUSHES out of the pump.
The radiator should have the connections at the bottom. That is, the way you have your rad in the diagram the connections should be at the bottom of the case i.e. not at the sides or the top, but rotated from the current position at 180 degrees
I wouldn't mount at flat on the bottom of the case cause you won't get a good intake of air, unless you raise the case off the floor a bit. And you'll also get lots of fluff off your floor.
Res's can be as cheap or expensive as you want. You can just get a water tight container or a near water tight container and seal it up. Most people used a tupperware tub and make holes in it and then seal it. I bought the Danger Den res cos it's neat and has a screw top to easily add water. It's like £20 or something - not very expensive.