Consistency matters more than brand. Choose a brand that works and stick with it till you get the hang of it.
Brushes
Keep it minimal, these are enough for almost everything:
A large hake or mop brush for washes
A med-large round brush (your primary brush - natural hair or mixed, avoid synthetic-only brush if possible).
A small brush for details
The goal is to use one primary brush for most of your painting. Over time, it becomes an extension of your hand, and builds intuitiveness with water control, pigment loading and strokes.
Colours
You only need 6 colours maximum (for most of my paintings I use just 3-4).
Core Palette:
Blues (Warm & Cool):
Ultramarine Blue
Cobalt Blue
Reds:
Crimson Lake/ Permanent Rose / Rose Madder (preferred over Alizarin)
Yellows (Warm & Cool):
Yellow Ochre or Raw Sienna
Transparent Yellow / Aureolin / Indian Yellow
Burnt Sienna
Colour Selection Tips
Choose transparent, single-pigment colours wherever possible
Avoid opaque & semi opaque pigments
Avoid colours made of more than 1 pigment. E.g. sap green (3 pigments)
A limited palette leads to colour harmony and fewer pigments overall creates cleaner mixes
Avoid cake/pan sets. Prefer professional watercolour tubes.