Art supplies.
A box of really decent colour pencils e.g. Faber Castell. Their Albrecht Durer range of watercolour pencils are very nice. IIRC the box of 12 should be around the £20 mark, as I bought one for a friend's (slightly older) daughter a couple of years ago.
Or how about a travelling box of 12 Winsor & Newton student (Cotman) watercolour half pans plus a couple of nice brushes (ProArte Polar are good) and a small pad of "postcard" NOT paper?
For both pencils & paint, you can then buy individual replacements from any decent art supplier, either bricks & mortar or online. And you can add to the selection later etc.