It would probably be more efficient in your training if you were to get 95 pray for turmoil instead of 96 herblore.
Agreed. Overloads are usesless on a pure; you might as well just get to 88 for Extreme Strength (with Greenman's Ale (m) and a reasonable 1-level buffer to complete 14 potions before the boost runs out) and stop there.
For prices, see this: http://runescape.wikia.com/wiki/Calculators/Potions and http://runescape.wikia.com/wiki/Calculators/Extreme_potions
EDIT: However, getting 95 prayer means you need turmoil, which requires a long series of quests and will get you to 30 or so defense.







