how big does a water pump need to be?

i an building a 3 -18 gallon tote dwc system,1 will be resovior,2 will hold plants.i want the pump to recirculate the water and feed drip lines.i wasnt sure if a 200 gph would be enough or do i need a 400 or 600 gph?

You won't need much to feed two lines/buckets. 200gph will work just fine.