-preferably a "block". Good ones are at least 140lb. Arches and Strathmore 400 series are recommended brands. 100% cotton is good too but can be expensive.
-pads are ok. Strathmore 400 series has spiral bound pads that are pretty good (brown front cover)
-sheets are also ok. Arches has 140lb, 100% cotton sheets that come in sizes as big as 22x30 inches.
-it might also be fun to try a 300lb paper
- tubes are more versatile, better pigment load and more colors. You can get a cheaper basic colors set and then get higher quality individual tubes of colors that you will use more, like a variety of browns, greens and pale colors. You'll get a better feel for colors you like to use after painting a few pieces. Recommended brands: M.Graham and Sennelier are honey-based, Daniel Smith, Winsor Newton.
-it might be fun to try pan watercolors. I use both types in one painting most of the time. Recommended brands: Kuretake Gansai Tambi and Winsor Newton Cotman
-"round" brushes are commonly used. Synthetic vs. Natural - when you get synthetic, make sure they are watercolor brushes, it should be labelled. You want ones that can hold a good amount of water and pigment but also comes to a nice point and has good spring. Natural watercolor brushes tend to be more expensive, they're usually made of either kolinsky or sable or a mix.
-"wash" or "flat" brushes are useful for filling bigger areas.
-pick up different sizes
-recommended brands: Princeton and Winsor Newton
-porcelain, glass, metal are best
-plastic works too