I use various good quality watercolour papers, usually 300 gsm (grams per square meter) so that they do not distort when wet. I prefer working on watercolour blocks with gummed edges such as those produced by Winsor and Newton, Saunders Waterford, Fluid and Arches.
I use sketchbooks published by Moleskine, Strathmore, Seawhite and others, again only using those with good-quality watercolour paper.
I use a mixture of Winsor and Newton (W&N) and Daniel Smith (DS) watercolours and during 2018 I decided to use Jane Blundell's Ultimate Mixing Palette. Jane's blog is a wonderful resource for anyone interested in pigments and watercolour brands. She has provided swatches of virtually every paint from every manufacturer and is an expert on the pigments and binders which go to make every shade on the shade cards! The idea of the Ultimate Mixing Palette is to provide a set of single pigment colours which between them will mix any possible shade of colour. This is backed up by pages on her blog and also in her book of printed mixes, The Ultimate Mixing Palette: A World of Colours which although expensive is an invaluable resource for anyone who is serious about colour.
I have however added to Jane's palette Winsor and Newton Light Red and Raw Sienna which are irreplaceable colours to me. I've tried other Raw Siennas but the W&N has a particular quality of light and luminance which think is unique. Although I can mix the Light Red, I use it so often that its worth me having it in my palette ready to use - Light Red is a basic colour for all brickwork and for mixing with French Ultramarine to make a vast range of greys.
Butt Titanium is very useful for buildings - particular the many buildings in the Loire Valley made of Loire Stone and also London buildings made of Portland stone.
Lunar Black is another really useful colour - so heavily granulating which I love, and also great for things like car tyres or other patches of deep, matt black.
I find that sable brushes hold a little too much water for my small paintings and so prefer either nylon brushes or a sable/synthetic mix. At the moment I have a set from Rosemary and Co of sable/synthetics which are just fine but to be honest anything with a good point and fine watercolour hair is fine.