Lemon yellow or cad yellow light
Cadmium red light
Cobalt blue (nice to have, close to primary blue, but it is expensive
I use a few more colors, but you can mix just about every possible color with this limited palette. Some artists use fewer than these yellows, reds and blues.
Filberts (a flat brush that is rounded at the end)
Brights (flat at end)
Get sizes 4, 6, and 8 in each
Get bristle brushes to start in a moderate price range. Later you will need some softer ones.
My favorite brand is Silver Brush, Grand Prix
Small palette knife
Sketch Book (spiral)
Palette (palette paper, glass palette or wooden palette)
Odorless mineral spirits (Gamblin brand is the one I like, but there are others, like Turpenoid)