Plugs work fine, but potting soil is cheaper and nice if you like to grow in larger containers. For eight US dollars you can pick up a bag of Miracle Gro Seed Starting Mix. I've been using it for years with great success and I like that I can buy it anywhere and that it doesn't scream weed grower. If you like Fox Farm products pick up a bag of Light Warrior which is Fox Farm's seed starting mix. And for what its worth, I use city tap water and don't bother with pHing. However I only start seeds indoors. After 3-4 weeks I transplant outside in my organic garden. I know when mixing hydroponic nutrients that pH and filtered water is important but not so much when growing organically