Well, I tell you a secret, I think that maybe I could work better with gouache if it was a bit cheaper. The fact that each color costs about 5 $ makes that I'm too careful and I'm not testing or improvising too much. The mixtures are difficult to make and if you take a lot of color and then you have to throw it away that hurts... Yes, that is maybe a silly point but at the moment unfortunately it's important.
And after gouache came watercolor. You just need regular water and watercolor (I've paid for 15 colors about 20 $), and I don't use a lot of color. It's also a difficult technique but as I can do as many tests as I want, without feeling so bad about the costs, I feel I can improve faster.
We have to do scientific painting. We have to imagine that we are explorers and we find a new animal or plant species and draw it in our journal... Here is my evolution from the first to the last work till now: