A #2 and #5B pencil is good enough for sketching.
For brushes I use Winsor & Newton Sceptre Gold II watercolor brushes (short handle) sizes 2 – 14. These are a synthetic/natural mix. Robert Simmons makes good, economical brushes: synthetic, synthetic/natural mix, or all natural sable.
I use Arches 140 lb. Bright White cold pressed 22” x 30” sheets. (I also buy the 156 lb, cold pressed rolls that are 10 yds. long and 51 inches wide and cut pieces to size.)
Lanaguarelle and Fabriano are brands I use also.
When purchasing paints I always get professional-grade tubes instead of student-grade (not Cotman, for instance). Student grade paint has fillers instead of pigment. Some brands I use are Old Holland, Winsor & Newton, and Holbein. Call or email the company for their color-fastness and color-intensity charts.
Flat brushes for large area washes, kneaded erasers, hair blower, Krylon Workable Fixatif, Golden Golden UV resistant medium, tracing paper, masking fluid, plywood board, water pan (to soak watercolor paper) staple gun & staples, pliers, and a screwdriver (to remove the staples from my board).
Just experiment and adjust your materials according to your preference.
This is my color palette: