you are off to a great start. I make both dairy and coconut water kefir. both are excellent for you. if you like it, you can switch over to real kefir grains... which you can get free or at little cost... then you never have to buy them again. the started culture will run out, then you have to buy it gain... besides, the grains have more strains of critters in them. If you google "dom's kefir site" you discusses this subject quite a bit.
for the coconut water, you can use either water grains or normal milk grains. if you use the milk grains, it will change them a bit, so after that you should not share them with others as "milk grains"..... but it will work for you.