After watching demo on Youtube and reading reviews, I’ve decided to buy Sakura Koi Watercolor which comes with a water brush.
I tried coloring this page of leaves from the coloring pad I bought earlier but the paper is quite thin and it warps as I color. Maybe this is why artist use special watercolor paper to make sure the final result would last better.
It was quite fast coloring using watercolor compared when I use other mediums like pen or colored pencils. It took me about 4 days to complete the whole leaves and the background.