How much quantity should I use ov Kojic acid, Arbutin and vitamin C powders in my daily use lotion,I really hv vry dark and dull complexion,it troubles me a lot,

It depends, this is the usual recommended dosage. But, I also believe that it depends on your skin complexion and the number of shades that you are trying to lighten, personally, as I would use at higher concentrations... except for the kojic as it tends to sting as it exfoliates.

Vitamin C (L-ascorbic acid): 0.2-4%
Kojic Acid: 1-3%
Arbutin (from bearberry): depends, as there is alpha-arbutin and beta-arbutin, alpha- being more potent.