You will need quality brushes. They really make the difference. You will need three or four round brushes: a number 12 will be used for large washes, a number 10 and a number 6 for intermediate layers of colour and a number 2 rigger for details. Promise yourself to always clean your brushes after every use. If you regularly do so, they will be faithful companions for years to come.
Using watercolour paper is essential if you want good results with this medium. A stack of rough 300 g/m2 paper is an excellent starting point. Don’t be afraid to begin with a large format: 30x40 cm is good enough. You will have enough space to paint comfortably with fluid movements.
Godet watercolours are fine to begin with, they are not very expensive and they are perfect for practise. Tube watercolours, on the other hand, have more pigment and are brighter. You will need a bit of experience to understand what colours you like better, according to your preferences and taste.