The motif was inspired by a painting of Cézanne's showing 3 apples that was my screen background. I could look at Cézanne's paintings all day, but Kandinsky comes close second!
Paper for acrylics - any size, this aquadoodle is 36x48 but not painted to the edges. I don't recommend that because the paper will buckle. Otherwise it needs no stretching. You can of course use thick watercolour paper, but it's far more expensive. Aquadoodles are studies.
Graphite and coloured pencils (you can also use charcoal or dry pastel, but there's none on this painting).
Watercolours (preferably out of tubes on a large mixing area)
Watercolour pencils (I use them instead of coloured pencil, but they smudge so you need to decide if you want that!)
Oil pastels. Be careful here. You can use water-soluble ones, but they do not repel water. That effect can only be achieved with normal oil pastels and with a candle (I used a white candle here). My oilpastels include neon colours that produce very dramatic effects.
You could use ink, but there's none on this aquadoodle.
Tools vary. Interesting painting knives make great marks, combs, scrapers (e.g. a credit card), sandpaper to diffuse dust from watercolour pencils. I used a painting knife for this, but you can also use a craft knife, which is also useful for sharpening pencils.
You could also use stencils, but I didn't here.
Spattering happens either accidentally or when you tap the side of a loaded paintbrush - to get a defined location, mask out the rest. You can use an old toothbrush for spattering effects, but I don#t as I usually get more on me that on the paper!