I would not use salt at all, salt is bad, because it creates sludge and scum in the water. Heres a picture with the salt water after enectrolysis test:
That was 10 litres of distilled water with only 2 teaspoonns of salt added.
The water tends to purify itself after a while. So do not use salt. If you want to increase the conductivity of the water, the best thing I have found is phosphoric acid ( food grade ). You need only a half of teaspoon added to 3 litres of water to increase the amp draw form 0.1 to 1A at 12V. You could also use vinegar, bet you will need to add very much of it to acheive the same amp draw, so that your water will "go bad". But for what I know, Meyer used distilled water and no electrolyte, he wanted the water potentialized with no current, only high voltage.