Slot 1 : LAVA (Alternate runes if needed in approx order of profit : WATER 20/30 or NATURE 29/30).
Slot 2 : DUST, EARTH(1) or EARTH(2) (Alternate runes if needed in approx order of profit : MIND 29/30 instead of dust 30/30; later ? instead of earth(1) 30/30; later ? instead of earth(2) 30/30)
Slot 1 : DUST (Alternate runes if needed in approx order of profit : MIND 29/30 or WATER 28/30).
Slot 2 : LAVA, AIR or FIRE (Alternate runes if needed in approx order of profit : MIND 23/30, BLOOD 28/30 or CHAOS 16/30 instead of lava 30/30; later ? instead of air 30/30; later ? instead of fire 30/30; more updates are welcome).
Tuesday's vis wax combination for the "Rune Goldberg Machine" is:
1st. Slot: MUD rune (replace with SOUL rune for 25/30 or CHAOS rune for 21/30)
2nd. Slot: Option A: AIR rune (cheap enough so no replacement needed)
2nd. Slot: Option B: ASTRAL rune (replace with WATER rune for ??/30)
2nd. Slot: Option C: LAW rune (replace with CHAOS rune for ??/30)
3rd. Slot: random rune for every player
you may also go to runescape.wikia and look up "Rune_Goldberg_Machine" for the true cost of each rune.