Happy birthday, ACD! I hope it's still your birthday in your country! 
I'm out of likes, but everyone have a heart 
@Ceru I love them! Specially the first one with the strong light and dark contrast. Yes, there are watercolour in tubes, as you say it's a paste you have to dillute with water and then you can mix it. I don't know if there are cheap tubes or if they sell them; here in Spain art supplies shops tend to have the really expensive, professional stuff. I remember when I was in the Netherlands, and I also saw them in Berlin, there were these "general crafts" shops where you could buy all kinds of supplies in different qualities, but I still didn't see them here.
@Tesh thanks for the advice! I'll follow it
I love the effect of layering colours. When I first considered starting with colours, I always thought that I'd use oils, because I love how they look on classic oil paintings. But before I even started, something inside me said "Nope". But with watercolours, when I saw them at the store I felt I really wanted to try them. Do you guys also get that feeling? That some media "call you" at an instinctive level? (maybe I'm just crazy
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@Morlanwen: at the tips & resources thread there is a pdf book about drawing faces, and also general tips to draw a face. I used to do the same as you, started with the eye and then the rest of the face. But it's much better to start with the general face structure (the famous ball and reference lines) and then build on the details.