Look, if you guys are talking about building watercooling parts from scratch, like homemade waterblocks, that stuff takes patience and skill and might be too hard for someone that has never done anything similar before.
Now if you're just talking about buying pre-built parts and putting them together, that's so easy even a monkey with a pair of scissors could do it. List of stuff that's needed:
1.
Reservoir to contain the water, preferably big.
2. One or more
waterpumps and preferably something that can push at least 500litres/hour. Laing 12V pumps should be ok.
3.
Radiator to transfer the heat from the water to the air.
4.
Waterblock for the CPU and maybe also GPU, NB, SB, MOSFET
5.
Fittings for the pump, waterblocks, reservoir, radiator (should be cheap)
6.
Hoses to connect everything (Nothing smaller than 10mm OD / 7mm ID)
7.
Distilled water or (only if you really can't get distilled) demineralised water.
8.
Fans to improve the heat transfer. You can use low-speed (900RPM) fans if you get a big radiator.
Make sure that the radiator and waterblocks are made of the same type metal (copper or aluminium) or you could face serious problems with corrosion. There are anti-corrosion agents that you can mix into the water, but it's better to be on the safe side.
When mixing the water use 30ml anti-algae fluid and one teaspoon of rinse-aid to help break the surface tension of the water.