I would add to the above recommendation of the Moira Huntly, which I found at a second hand book dealer's a while back.
She makes an interesting suggestion for the base layer of paint, mixing it with a little acrylic glaze (Daler Rowney make this), so you can play around with pure gouache layers over the top. I haven't tried this yet, as I'm a beginner in this medium too. I've seen 'acrylic gouache' available in Jackson's catalogue, but I have no idea what it's like, and it may just be another type of acrylic paint.
When I have some disposable cash, I'm going to try Schminke Horadam gouache. It has more permanence than the various brands of 'designer' gouache, including Schminke's own. (Also, I think 'designer's gouache' smells awful. Are you listening, Winsor and Newton?!) M Graham also make a real 'artist's gouache'. I'll have to give that a miss, because the pound has fallen so far in relation to the dollar that I can no longer afford to import art materials from the US.