Water Blocks (CPU, GPU Optional)
Pump, Grab a D5
Reservoir (many options)
Tubing. Comes in many sizes.
Radiator - 120, 240, 360, 480 (Basically go for 120mm per block minimum)
Fittings, (Barbs or Compression fittings, 2 per item) - Keep in mind if you use compression fittings you'll need to know both Inside Diameter ID and Outside Diameter OD of your tubing.
Check out
Dazmode - Canadian Watercooling Store, Reviews and Community and watch his videos and check out the premade kits he's got listed they'll tell you a lot of info about what to get.