well its seems good though, to get everything cheap, but den again i wonder whats the main factors to look for DIY liquid cooling system? beside the water pump he has mention
Plenty.
Pump is just part of it. If a weak pump is used, you cant get coolant moving fast enough to cool your components. Not forgetting the restrictive rads.
Tubings - plasticizer issues
Coolant - bad coolant can lead to gunks, and can stain tubings and other components also.
Radiators - full copper or half brass, or alu, this will determine your cooling performance also. The amount of radiator size and thickness, the fins per inch, the physical restrictions of the case, the restricted flow, all this will determine how much cooling capacity you will have. And also will see how much you really need when cooling a couple of gpus and a single cpu.
Fans - the fans that pushes through that dense fin radiator. A bad fan will never be able to cool those dense fins.
Reservoir - none, just to look cool.
Fittings - bad fittings can cause leaks. Especially when oring is worn or broken.
Waterblocks - whether is made of copper, nickel plated, derlin, or some other form of heat conductor. This is critical cause it is responsible to conduct as much heat as possible and also to dissipate/channel heat away with moving coolant to the heat exchanger (aka radiator)