QUALITY -- I am definitely an advocate of using good supplies -- especially good paint! Please don't sacrifice quality for the sake of economy. I know! Watercolor pigments are expensive, but consider how long they last. Watercolor pigments are used up at a much slower rate than oil or acrylic colors. So, don't worry -- you won't be racing through your tubes of paint as you might in an oil painting class. With proper care, your paints will last a long time, which makes them economical to use after all. Scrimping on paints is generally not worth it.
As a child, you probably played with watercolors -- most likely using the paints that came in the little metal box with a lid, containing the 6 round or square little cakes of paint. Our early, sometimes-unhappy, results in watercolor usually stemmed from using this small set of paints and a crappy little brush. Now, it's time to upgrade to watercolors in tubes, that produce brilliant colors, and a palette with room for mixing large washes of color (and a not-so-crappy brush).