Round brushes are your usual go-to paint brush for doing watercolor. They are great for doing thick to thin lines in the same stroke depending on the amount of pressure applied to them from the hand. They have a fine tip that allows for you to be able to do detail work as well as thick broad strokes. The smaller the number, the smaller the brush size.
Synthetic Sable Paint Brushes are the perfect go-to for any level of artist. Synthetic brushes are perfect for watercolor and gouache because they last longer than natural hair brushes and the bristles don't fall out while painting.
Proper care tips: Make sure to clean your brushes well after each use (with water) and only use these brushes with watercolor and gouache.