A wide range of flavours is essential, or you're always short of one you need to realise that perfect idea. I started with 30 flavours, and have now added to/replaced a lot with 37 of the Fantasy Fudge range, so I have about 60 different flavours. There are some that get used a LOT more than others (few of my blends are without a toffee/butterscotch ingredient).
I'm in the process of developing some recipes to start using some of the more unusual flavours (such as Rose, Lavender & Violet).
New recipes over the weekend were:
Apple, Gingerbread, Toffee & Cream
Tropical Fruits, Coconut & a touch of aniseed (trying to strike that subtle balance of a hint of aniseed without overwhleming the whole blend).
I have tested both, but I think these are blends that definitely benefit from some steeping before I make a final assessment.