Cassart and JacksonArt are two reliable providers of art supplies. Cassart is usually a bit cheaper but unfortunately at the moment they are low on a lot if their essential supplies.
Acrylic paint
Essential
Titanium white
Cadmium yellow hue
Crimson
Prussian blue
Cobalt blue hue
If keen you can also get cadmium red hue
Unfortunately there is no purple in this range so you will have to mix it ūüėČ
Soft pastels 
Set of 32
Charcoal
Oil pastels
Ink
The 150 mill bottle would suffice
 
Cartridge paper 
https://www.jacksonsart.com/winsor-newton-cartridge-gummed-pad-130gsm-medium-30-sheets-a2       This is probably best value I have seen, A2 size so you can cut it and will last you a while
https://www.jacksonsart.com/daler-rowney-cartridge-pads      This is A3, a bit heavier ( the heavier the better) but comes out a bit more expensive