Positive print stock is always a good entry for the experienced as well as the beginner. Labs have print film in stock. Non-sensitised but of fine graininess and not expensive, developed in three to four minutes, you can see what a lens is delivering, how accurately you focus, how lighting might be improved, whether the whole setup is worthwhile.
Print films are not made to a given exposure index, therefore batches vary in sensitivity. Generally they are around ISO 8 to 10.
I agree that slow stocks are missing. Manufacturers have let themselves carry away from the real/reel thing which is how 16-mm. cinematography had begun. FOMA BOHEMIA could make a Fomapan R 20. That would be most welcome.