Where can I find the rules?
http://www.bombjack.org/commodore/amiga/games/Elixir_of_Life_Manual.pdf

The table is at the bottom of page 2. When brewing, add the cost of your gem(s) to the dice roll. On a 3 or less, the brewing fails and you lose the ingredients. On a 4 or 5, nothing happens but you can attempt to brew again on your next turn. Finally, on a 6+, the potion is successfully brewed.