I started my first grow just like you and bought everything I needed at Lowes/Home Depot.

I am using a 17-17-17 Peter's All Purpose Plant food. It's like $12 at Homedepot or Lowes. I forgot where I got it. I just started feeding the nutes and I'm in week 4 of veg. It might have been just a little bit early as I got one plant turning very light yellow on a couple tips but I drained it and it should be fine soon. The food mix is just mixed in with one gallon of water. You can buy distilled water at Wal Mart for about .79 cents a gallon.