I just used cheap pine... About a $1/ft at the place I get my wood. It's 10" wide, so I glue it up. It's light and there wasn't a lot of fine detail that can break off in the machining. The paint pretty much covers the small knots.
The great part is that Michael Tyler (for Vectric products) is including painting instructions in his latest videos. It turns a plain piece into something spectacular. He's very good at what he does. 'Ya can't beat that for free.