I would say bolt, since its alot cheaper and still hits high with the gaunts, but if you have the money and want to save time, wave would be fine. As for doses, its roughly 3 for every 250 fire bolts for me, but I'm sure someone else can give you something more accurate. And really, its not a huge cash loss, since compared to alching you're getting charms, hp xp, prayer xp, cash from alchs, blood/soul runes, clues (I average one per trip), and loads of time to relax, instead of constant clicking.